The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 951531691c4bcaa59f56a316e018bc2ff1ddf855 Mon Sep 17 00:00:00 2001
From: "Isaac J. Manjarres" <isaacm(a)codeaurora.org>
Date: Tue, 13 Aug 2019 15:37:37 -0700
Subject: [PATCH] mm/usercopy: use memory range to be accessed for wraparound
check
Currently, when checking to see if accessing n bytes starting at address
"ptr" will cause a wraparound in the memory addresses, the check in
check_bogus_address() adds an extra byte, which is incorrect, as the
range of addresses that will be accessed is [ptr, ptr + (n - 1)].
This can lead to incorrectly detecting a wraparound in the memory
address, when trying to read 4 KB from memory that is mapped to the the
last possible page in the virtual address space, when in fact, accessing
that range of memory would not cause a wraparound to occur.
Use the memory range that will actually be accessed when considering if
accessing a certain amount of bytes will cause the memory address to
wrap around.
Link: http://lkml.kernel.org/r/1564509253-23287-1-git-send-email-isaacm@codeauror…
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Prasad Sodagudi <psodagud(a)codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm(a)codeaurora.org>
Co-developed-by: Prasad Sodagudi <psodagud(a)codeaurora.org>
Reviewed-by: William Kucharski <william.kucharski(a)oracle.com>
Acked-by: Kees Cook <keescook(a)chromium.org>
Cc: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Cc: Trilok Soni <tsoni(a)codeaurora.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 2a09796edef8..98e924864554 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -147,7 +147,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
bool to_user)
{
/* Reject if object wraps past end of memory. */
- if (ptr + n < ptr)
+ if (ptr + (n - 1) < ptr)
usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n);
/* Reject if NULL or ZERO-allocation. */
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 951531691c4bcaa59f56a316e018bc2ff1ddf855 Mon Sep 17 00:00:00 2001
From: "Isaac J. Manjarres" <isaacm(a)codeaurora.org>
Date: Tue, 13 Aug 2019 15:37:37 -0700
Subject: [PATCH] mm/usercopy: use memory range to be accessed for wraparound
check
Currently, when checking to see if accessing n bytes starting at address
"ptr" will cause a wraparound in the memory addresses, the check in
check_bogus_address() adds an extra byte, which is incorrect, as the
range of addresses that will be accessed is [ptr, ptr + (n - 1)].
This can lead to incorrectly detecting a wraparound in the memory
address, when trying to read 4 KB from memory that is mapped to the the
last possible page in the virtual address space, when in fact, accessing
that range of memory would not cause a wraparound to occur.
Use the memory range that will actually be accessed when considering if
accessing a certain amount of bytes will cause the memory address to
wrap around.
Link: http://lkml.kernel.org/r/1564509253-23287-1-git-send-email-isaacm@codeauror…
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Prasad Sodagudi <psodagud(a)codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm(a)codeaurora.org>
Co-developed-by: Prasad Sodagudi <psodagud(a)codeaurora.org>
Reviewed-by: William Kucharski <william.kucharski(a)oracle.com>
Acked-by: Kees Cook <keescook(a)chromium.org>
Cc: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Cc: Trilok Soni <tsoni(a)codeaurora.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 2a09796edef8..98e924864554 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -147,7 +147,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
bool to_user)
{
/* Reject if object wraps past end of memory. */
- if (ptr + n < ptr)
+ if (ptr + (n - 1) < ptr)
usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n);
/* Reject if NULL or ZERO-allocation. */
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 6051d3bd3b91e96c59e62b8be2dba1cc2b19ee40 Mon Sep 17 00:00:00 2001
From: Henry Burns <henryburns(a)google.com>
Date: Tue, 13 Aug 2019 15:37:21 -0700
Subject: [PATCH] mm/z3fold.c: fix z3fold_destroy_pool() ordering
The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.
If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:
z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*
So compact_wq needs to be destroyed before release_wq.
Link: http://lkml.kernel.org/r/20190726224810.79660-1-henryburns@google.com
Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns(a)google.com>
Reviewed-by: Shakeel Butt <shakeelb(a)google.com>
Reviewed-by: Jonathan Adams <jwadams(a)google.com>
Cc: Vitaly Vul <vitaly.vul(a)sony.com>
Cc: Vitaly Wool <vitalywool(a)gmail.com>
Cc: David Howells <dhowells(a)redhat.com>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Cc: Al Viro <viro(a)zeniv.linux.org.uk
Cc: Henry Burns <henrywolfeburns(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 1a029a7432ee..43de92f52961 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
kmem_cache_destroy(pool->c_handle);
z3fold_unregister_migration(pool);
- destroy_workqueue(pool->release_wq);
+
+ /*
+ * We need to destroy pool->compact_wq before pool->release_wq,
+ * as any pending work on pool->compact_wq will call
+ * queue_work(pool->release_wq, &pool->work).
+ */
+
destroy_workqueue(pool->compact_wq);
+ destroy_workqueue(pool->release_wq);
kfree(pool);
}
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 6051d3bd3b91e96c59e62b8be2dba1cc2b19ee40 Mon Sep 17 00:00:00 2001
From: Henry Burns <henryburns(a)google.com>
Date: Tue, 13 Aug 2019 15:37:21 -0700
Subject: [PATCH] mm/z3fold.c: fix z3fold_destroy_pool() ordering
The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.
If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:
z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*
So compact_wq needs to be destroyed before release_wq.
Link: http://lkml.kernel.org/r/20190726224810.79660-1-henryburns@google.com
Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns(a)google.com>
Reviewed-by: Shakeel Butt <shakeelb(a)google.com>
Reviewed-by: Jonathan Adams <jwadams(a)google.com>
Cc: Vitaly Vul <vitaly.vul(a)sony.com>
Cc: Vitaly Wool <vitalywool(a)gmail.com>
Cc: David Howells <dhowells(a)redhat.com>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Cc: Al Viro <viro(a)zeniv.linux.org.uk
Cc: Henry Burns <henrywolfeburns(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 1a029a7432ee..43de92f52961 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
kmem_cache_destroy(pool->c_handle);
z3fold_unregister_migration(pool);
- destroy_workqueue(pool->release_wq);
+
+ /*
+ * We need to destroy pool->compact_wq before pool->release_wq,
+ * as any pending work on pool->compact_wq will call
+ * queue_work(pool->release_wq, &pool->work).
+ */
+
destroy_workqueue(pool->compact_wq);
+ destroy_workqueue(pool->release_wq);
kfree(pool);
}
The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From a53190a4aaa36494f4d7209fd1fcc6f2ee08e0e0 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi(a)linux.alibaba.com>
Date: Tue, 13 Aug 2019 15:37:18 -0700
Subject: [PATCH] mm: mempolicy: handle vma with unmovable pages mapped
correctly in mbind
When running syzkaller internally, we ran into the below bug on 4.9.x
kernel:
kernel BUG at mm/huge_memory.c:2124!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 1518 Comm: syz-executor107 Not tainted 4.9.168+ #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.5.1 01/01/2011
task: ffff880067b34900 task.stack: ffff880068998000
RIP: split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124
Call Trace:
split_huge_page include/linux/huge_mm.h:100 [inline]
queue_pages_pte_range+0x7e1/0x1480 mm/mempolicy.c:538
walk_pmd_range mm/pagewalk.c:50 [inline]
walk_pud_range mm/pagewalk.c:90 [inline]
walk_pgd_range mm/pagewalk.c:116 [inline]
__walk_page_range+0x44a/0xdb0 mm/pagewalk.c:208
walk_page_range+0x154/0x370 mm/pagewalk.c:285
queue_pages_range+0x115/0x150 mm/mempolicy.c:694
do_mbind mm/mempolicy.c:1241 [inline]
SYSC_mbind+0x3c3/0x1030 mm/mempolicy.c:1370
SyS_mbind+0x46/0x60 mm/mempolicy.c:1352
do_syscall_64+0x1d2/0x600 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: c7 80 1c 02 00 e8 26 0a 76 01 <0f> 0b 48 c7 c7 40 46 45 84 e8 4c
RIP [<ffffffff81895d6b>] split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124
RSP <ffff88006899f980>
with the below test:
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
intptr_t res = 0;
res = syscall(__NR_socket, 0x11, 3, 0x300);
if (res != -1)
r[0] = res;
*(uint32_t*)0x20000040 = 0x10000;
*(uint32_t*)0x20000044 = 1;
*(uint32_t*)0x20000048 = 0xc520;
*(uint32_t*)0x2000004c = 1;
syscall(__NR_setsockopt, r[0], 0x107, 0xd, 0x20000040, 0x10);
syscall(__NR_mmap, 0x20fed000, 0x10000, 0, 0x8811, r[0], 0);
*(uint64_t*)0x20000340 = 2;
syscall(__NR_mbind, 0x20ff9000, 0x4000, 0x4002, 0x20000340, 0x45d4, 3);
return 0;
}
Actually the test does:
mmap(0x20000000, 16777216, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000
socket(AF_PACKET, SOCK_RAW, 768) = 3
setsockopt(3, SOL_PACKET, PACKET_TX_RING, {block_size=65536, block_nr=1, frame_size=50464, frame_nr=1}, 16) = 0
mmap(0x20fed000, 65536, PROT_NONE, MAP_SHARED|MAP_FIXED|MAP_POPULATE|MAP_DENYWRITE, 3, 0) = 0x20fed000
mbind(..., MPOL_MF_STRICT|MPOL_MF_MOVE) = 0
The setsockopt() would allocate compound pages (16 pages in this test)
for packet tx ring, then the mmap() would call packet_mmap() to map the
pages into the user address space specified by the mmap() call.
When calling mbind(), it would scan the vma to queue the pages for
migration to the new node. It would split any huge page since 4.9
doesn't support THP migration, however, the packet tx ring compound
pages are not THP and even not movable. So, the above bug is triggered.
However, the later kernel is not hit by this issue due to commit
d44d363f6578 ("mm: don't assume anonymous pages have SwapBacked flag"),
which just removes the PageSwapBacked check for a different reason.
But, there is a deeper issue. According to the semantic of mbind(), it
should return -EIO if MPOL_MF_MOVE or MPOL_MF_MOVE_ALL was specified and
MPOL_MF_STRICT was also specified, but the kernel was unable to move all
existing pages in the range. The tx ring of the packet socket is
definitely not movable, however, mbind() returns success for this case.
Although the most socket file associates with non-movable pages, but XDP
may have movable pages from gup. So, it sounds not fine to just check
the underlying file type of vma in vma_migratable().
Change migrate_page_add() to check if the page is movable or not, if it
is unmovable, just return -EIO. But do not abort pte walk immediately,
since there may be pages off LRU temporarily. We should migrate other
pages if MPOL_MF_MOVE* is specified. Set has_unmovable flag if some
paged could not be not moved, then return -EIO for mbind() eventually.
With this change the above test would return -EIO as expected.
[yang.shi(a)linux.alibaba.com: fix review comments from Vlastimil]
Link: http://lkml.kernel.org/r/1563556862-54056-3-git-send-email-yang.shi@linux.a…
Link: http://lkml.kernel.org/r/1561162809-59140-3-git-send-email-yang.shi@linux.a…
Signed-off-by: Yang Shi <yang.shi(a)linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mel Gorman <mgorman(a)techsingularity.net>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 932c26845e3e..547cd403ed02 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -403,7 +403,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
},
};
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags);
struct queue_pages {
@@ -463,12 +463,11 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
flags = qp->flags;
/* go to thp migration */
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
- if (!vma_migratable(walk->vma)) {
+ if (!vma_migratable(walk->vma) ||
+ migrate_page_add(page, qp->pagelist, flags)) {
ret = 1;
goto unlock;
}
-
- migrate_page_add(page, qp->pagelist, flags);
} else
ret = -EIO;
unlock:
@@ -532,7 +531,14 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
has_unmovable = true;
break;
}
- migrate_page_add(page, qp->pagelist, flags);
+
+ /*
+ * Do not abort immediately since there may be
+ * temporary off LRU pages in the range. Still
+ * need migrate other LRU pages.
+ */
+ if (migrate_page_add(page, qp->pagelist, flags))
+ has_unmovable = true;
} else
break;
}
@@ -961,7 +967,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
/*
* page migration, thp tail pages can be passed.
*/
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags)
{
struct page *head = compound_head(page);
@@ -974,8 +980,19 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON + page_is_file_cache(head),
hpage_nr_pages(head));
+ } else if (flags & MPOL_MF_STRICT) {
+ /*
+ * Non-movable page may reach here. And, there may be
+ * temporary off LRU pages or non-LRU movable pages.
+ * Treat them as unmovable pages since they can't be
+ * isolated, so they can't be moved at the moment. It
+ * should return -EIO for this case too.
+ */
+ return -EIO;
}
}
+
+ return 0;
}
/* page allocation callback for NUMA node migration */
@@ -1178,9 +1195,10 @@ static struct page *new_page(struct page *page, unsigned long start)
}
#else
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags)
{
+ return -EIO;
}
int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From a53190a4aaa36494f4d7209fd1fcc6f2ee08e0e0 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi(a)linux.alibaba.com>
Date: Tue, 13 Aug 2019 15:37:18 -0700
Subject: [PATCH] mm: mempolicy: handle vma with unmovable pages mapped
correctly in mbind
When running syzkaller internally, we ran into the below bug on 4.9.x
kernel:
kernel BUG at mm/huge_memory.c:2124!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 1518 Comm: syz-executor107 Not tainted 4.9.168+ #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.5.1 01/01/2011
task: ffff880067b34900 task.stack: ffff880068998000
RIP: split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124
Call Trace:
split_huge_page include/linux/huge_mm.h:100 [inline]
queue_pages_pte_range+0x7e1/0x1480 mm/mempolicy.c:538
walk_pmd_range mm/pagewalk.c:50 [inline]
walk_pud_range mm/pagewalk.c:90 [inline]
walk_pgd_range mm/pagewalk.c:116 [inline]
__walk_page_range+0x44a/0xdb0 mm/pagewalk.c:208
walk_page_range+0x154/0x370 mm/pagewalk.c:285
queue_pages_range+0x115/0x150 mm/mempolicy.c:694
do_mbind mm/mempolicy.c:1241 [inline]
SYSC_mbind+0x3c3/0x1030 mm/mempolicy.c:1370
SyS_mbind+0x46/0x60 mm/mempolicy.c:1352
do_syscall_64+0x1d2/0x600 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: c7 80 1c 02 00 e8 26 0a 76 01 <0f> 0b 48 c7 c7 40 46 45 84 e8 4c
RIP [<ffffffff81895d6b>] split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124
RSP <ffff88006899f980>
with the below test:
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
intptr_t res = 0;
res = syscall(__NR_socket, 0x11, 3, 0x300);
if (res != -1)
r[0] = res;
*(uint32_t*)0x20000040 = 0x10000;
*(uint32_t*)0x20000044 = 1;
*(uint32_t*)0x20000048 = 0xc520;
*(uint32_t*)0x2000004c = 1;
syscall(__NR_setsockopt, r[0], 0x107, 0xd, 0x20000040, 0x10);
syscall(__NR_mmap, 0x20fed000, 0x10000, 0, 0x8811, r[0], 0);
*(uint64_t*)0x20000340 = 2;
syscall(__NR_mbind, 0x20ff9000, 0x4000, 0x4002, 0x20000340, 0x45d4, 3);
return 0;
}
Actually the test does:
mmap(0x20000000, 16777216, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000
socket(AF_PACKET, SOCK_RAW, 768) = 3
setsockopt(3, SOL_PACKET, PACKET_TX_RING, {block_size=65536, block_nr=1, frame_size=50464, frame_nr=1}, 16) = 0
mmap(0x20fed000, 65536, PROT_NONE, MAP_SHARED|MAP_FIXED|MAP_POPULATE|MAP_DENYWRITE, 3, 0) = 0x20fed000
mbind(..., MPOL_MF_STRICT|MPOL_MF_MOVE) = 0
The setsockopt() would allocate compound pages (16 pages in this test)
for packet tx ring, then the mmap() would call packet_mmap() to map the
pages into the user address space specified by the mmap() call.
When calling mbind(), it would scan the vma to queue the pages for
migration to the new node. It would split any huge page since 4.9
doesn't support THP migration, however, the packet tx ring compound
pages are not THP and even not movable. So, the above bug is triggered.
However, the later kernel is not hit by this issue due to commit
d44d363f6578 ("mm: don't assume anonymous pages have SwapBacked flag"),
which just removes the PageSwapBacked check for a different reason.
But, there is a deeper issue. According to the semantic of mbind(), it
should return -EIO if MPOL_MF_MOVE or MPOL_MF_MOVE_ALL was specified and
MPOL_MF_STRICT was also specified, but the kernel was unable to move all
existing pages in the range. The tx ring of the packet socket is
definitely not movable, however, mbind() returns success for this case.
Although the most socket file associates with non-movable pages, but XDP
may have movable pages from gup. So, it sounds not fine to just check
the underlying file type of vma in vma_migratable().
Change migrate_page_add() to check if the page is movable or not, if it
is unmovable, just return -EIO. But do not abort pte walk immediately,
since there may be pages off LRU temporarily. We should migrate other
pages if MPOL_MF_MOVE* is specified. Set has_unmovable flag if some
paged could not be not moved, then return -EIO for mbind() eventually.
With this change the above test would return -EIO as expected.
[yang.shi(a)linux.alibaba.com: fix review comments from Vlastimil]
Link: http://lkml.kernel.org/r/1563556862-54056-3-git-send-email-yang.shi@linux.a…
Link: http://lkml.kernel.org/r/1561162809-59140-3-git-send-email-yang.shi@linux.a…
Signed-off-by: Yang Shi <yang.shi(a)linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mel Gorman <mgorman(a)techsingularity.net>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 932c26845e3e..547cd403ed02 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -403,7 +403,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
},
};
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags);
struct queue_pages {
@@ -463,12 +463,11 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
flags = qp->flags;
/* go to thp migration */
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
- if (!vma_migratable(walk->vma)) {
+ if (!vma_migratable(walk->vma) ||
+ migrate_page_add(page, qp->pagelist, flags)) {
ret = 1;
goto unlock;
}
-
- migrate_page_add(page, qp->pagelist, flags);
} else
ret = -EIO;
unlock:
@@ -532,7 +531,14 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
has_unmovable = true;
break;
}
- migrate_page_add(page, qp->pagelist, flags);
+
+ /*
+ * Do not abort immediately since there may be
+ * temporary off LRU pages in the range. Still
+ * need migrate other LRU pages.
+ */
+ if (migrate_page_add(page, qp->pagelist, flags))
+ has_unmovable = true;
} else
break;
}
@@ -961,7 +967,7 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
/*
* page migration, thp tail pages can be passed.
*/
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags)
{
struct page *head = compound_head(page);
@@ -974,8 +980,19 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON + page_is_file_cache(head),
hpage_nr_pages(head));
+ } else if (flags & MPOL_MF_STRICT) {
+ /*
+ * Non-movable page may reach here. And, there may be
+ * temporary off LRU pages or non-LRU movable pages.
+ * Treat them as unmovable pages since they can't be
+ * isolated, so they can't be moved at the moment. It
+ * should return -EIO for this case too.
+ */
+ return -EIO;
}
}
+
+ return 0;
}
/* page allocation callback for NUMA node migration */
@@ -1178,9 +1195,10 @@ static struct page *new_page(struct page *page, unsigned long start)
}
#else
-static void migrate_page_add(struct page *page, struct list_head *pagelist,
+static int migrate_page_add(struct page *page, struct list_head *pagelist,
unsigned long flags)
{
+ return -EIO;
}
int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From d883544515aae54842c21730b880172e7894fde9 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi(a)linux.alibaba.com>
Date: Tue, 13 Aug 2019 15:37:15 -0700
Subject: [PATCH] mm: mempolicy: make the behavior consistent when
MPOL_MF_MOVE* and MPOL_MF_STRICT were specified
When both MPOL_MF_MOVE* and MPOL_MF_STRICT was specified, mbind() should
try best to migrate misplaced pages, if some of the pages could not be
migrated, then return -EIO.
There are three different sub-cases:
1. vma is not migratable
2. vma is migratable, but there are unmovable pages
3. vma is migratable, pages are movable, but migrate_pages() fails
If #1 happens, kernel would just abort immediately, then return -EIO,
after a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when
MPOL_MF_STRICT is specified").
If #3 happens, kernel would set policy and migrate pages with
best-effort, but won't rollback the migrated pages and reset the policy
back.
Before that commit, they behaves in the same way. It'd better to keep
their behavior consistent. But, rolling back the migrated pages and
resetting the policy back sounds not feasible, so just make #1 behave as
same as #3.
Userspace will know that not everything was successfully migrated (via
-EIO), and can take whatever steps it deems necessary - attempt
rollback, determine which exact page(s) are violating the policy, etc.
Make queue_pages_range() return 1 to indicate there are unmovable pages
or vma is not migratable.
The #2 is not handled correctly in the current kernel, the following
patch will fix it.
[yang.shi(a)linux.alibaba.com: fix review comments from Vlastimil]
Link: http://lkml.kernel.org/r/1563556862-54056-2-git-send-email-yang.shi@linux.a…
Link: http://lkml.kernel.org/r/1561162809-59140-2-git-send-email-yang.shi@linux.a…
Signed-off-by: Yang Shi <yang.shi(a)linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mel Gorman <mgorman(a)techsingularity.net>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f48693f75b37..932c26845e3e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -429,11 +429,14 @@ static inline bool queue_pages_required(struct page *page,
}
/*
- * queue_pages_pmd() has three possible return values:
- * 1 - pages are placed on the right node or queued successfully.
- * 0 - THP was split.
- * -EIO - is migration entry or MPOL_MF_STRICT was specified and an existing
- * page was already on a node that does not follow the policy.
+ * queue_pages_pmd() has four possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * 2 - THP was split.
+ * -EIO - is migration entry or only MPOL_MF_STRICT was specified and an
+ * existing page was already on a node that does not follow the
+ * policy.
*/
static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
unsigned long end, struct mm_walk *walk)
@@ -451,19 +454,17 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
__split_huge_pmd(walk->vma, pmd, addr, false, NULL);
+ ret = 2;
goto out;
}
- if (!queue_pages_required(page, qp)) {
- ret = 1;
+ if (!queue_pages_required(page, qp))
goto unlock;
- }
- ret = 1;
flags = qp->flags;
/* go to thp migration */
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
if (!vma_migratable(walk->vma)) {
- ret = -EIO;
+ ret = 1;
goto unlock;
}
@@ -479,6 +480,13 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
/*
* Scan through pages checking if pages follow certain conditions,
* and move them to the pagelist if they do.
+ *
+ * queue_pages_pte_range() has three possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * -EIO - only MPOL_MF_STRICT was specified and an existing page was already
+ * on a node that does not follow the policy.
*/
static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
@@ -488,17 +496,17 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
struct queue_pages *qp = walk->private;
unsigned long flags = qp->flags;
int ret;
+ bool has_unmovable = false;
pte_t *pte;
spinlock_t *ptl;
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
ret = queue_pages_pmd(pmd, ptl, addr, end, walk);
- if (ret > 0)
- return 0;
- else if (ret < 0)
+ if (ret != 2)
return ret;
}
+ /* THP was split, fall through to pte walk */
if (pmd_trans_unstable(pmd))
return 0;
@@ -519,14 +527,21 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
if (!queue_pages_required(page, qp))
continue;
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
- if (!vma_migratable(vma))
+ /* MPOL_MF_STRICT must be specified if we get here */
+ if (!vma_migratable(vma)) {
+ has_unmovable = true;
break;
+ }
migrate_page_add(page, qp->pagelist, flags);
} else
break;
}
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
+
+ if (has_unmovable)
+ return 1;
+
return addr != end ? -EIO : 0;
}
@@ -639,7 +654,13 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
*
* If pages found in a given range are on a set of nodes (determined by
* @nodes and @flags,) it's isolated and queued to the pagelist which is
- * passed via @private.)
+ * passed via @private.
+ *
+ * queue_pages_range() has three possible return values:
+ * 1 - there is unmovable page, but MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * 0 - queue pages successfully or no misplaced page.
+ * -EIO - there is misplaced page and only MPOL_MF_STRICT was specified.
*/
static int
queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
@@ -1182,6 +1203,7 @@ static long do_mbind(unsigned long start, unsigned long len,
struct mempolicy *new;
unsigned long end;
int err;
+ int ret;
LIST_HEAD(pagelist);
if (flags & ~(unsigned long)MPOL_MF_VALID)
@@ -1243,10 +1265,15 @@ static long do_mbind(unsigned long start, unsigned long len,
if (err)
goto mpol_out;
- err = queue_pages_range(mm, start, end, nmask,
+ ret = queue_pages_range(mm, start, end, nmask,
flags | MPOL_MF_INVERT, &pagelist);
- if (!err)
- err = mbind_range(mm, start, end, new);
+
+ if (ret < 0) {
+ err = -EIO;
+ goto up_out;
+ }
+
+ err = mbind_range(mm, start, end, new);
if (!err) {
int nr_failed = 0;
@@ -1259,13 +1286,14 @@ static long do_mbind(unsigned long start, unsigned long len,
putback_movable_pages(&pagelist);
}
- if (nr_failed && (flags & MPOL_MF_STRICT))
+ if ((ret > 0) || (nr_failed && (flags & MPOL_MF_STRICT)))
err = -EIO;
} else
putback_movable_pages(&pagelist);
+up_out:
up_write(&mm->mmap_sem);
- mpol_out:
+mpol_out:
mpol_put(new);
return err;
}
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From d883544515aae54842c21730b880172e7894fde9 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi(a)linux.alibaba.com>
Date: Tue, 13 Aug 2019 15:37:15 -0700
Subject: [PATCH] mm: mempolicy: make the behavior consistent when
MPOL_MF_MOVE* and MPOL_MF_STRICT were specified
When both MPOL_MF_MOVE* and MPOL_MF_STRICT was specified, mbind() should
try best to migrate misplaced pages, if some of the pages could not be
migrated, then return -EIO.
There are three different sub-cases:
1. vma is not migratable
2. vma is migratable, but there are unmovable pages
3. vma is migratable, pages are movable, but migrate_pages() fails
If #1 happens, kernel would just abort immediately, then return -EIO,
after a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when
MPOL_MF_STRICT is specified").
If #3 happens, kernel would set policy and migrate pages with
best-effort, but won't rollback the migrated pages and reset the policy
back.
Before that commit, they behaves in the same way. It'd better to keep
their behavior consistent. But, rolling back the migrated pages and
resetting the policy back sounds not feasible, so just make #1 behave as
same as #3.
Userspace will know that not everything was successfully migrated (via
-EIO), and can take whatever steps it deems necessary - attempt
rollback, determine which exact page(s) are violating the policy, etc.
Make queue_pages_range() return 1 to indicate there are unmovable pages
or vma is not migratable.
The #2 is not handled correctly in the current kernel, the following
patch will fix it.
[yang.shi(a)linux.alibaba.com: fix review comments from Vlastimil]
Link: http://lkml.kernel.org/r/1563556862-54056-2-git-send-email-yang.shi@linux.a…
Link: http://lkml.kernel.org/r/1561162809-59140-2-git-send-email-yang.shi@linux.a…
Signed-off-by: Yang Shi <yang.shi(a)linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Mel Gorman <mgorman(a)techsingularity.net>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f48693f75b37..932c26845e3e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -429,11 +429,14 @@ static inline bool queue_pages_required(struct page *page,
}
/*
- * queue_pages_pmd() has three possible return values:
- * 1 - pages are placed on the right node or queued successfully.
- * 0 - THP was split.
- * -EIO - is migration entry or MPOL_MF_STRICT was specified and an existing
- * page was already on a node that does not follow the policy.
+ * queue_pages_pmd() has four possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * 2 - THP was split.
+ * -EIO - is migration entry or only MPOL_MF_STRICT was specified and an
+ * existing page was already on a node that does not follow the
+ * policy.
*/
static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
unsigned long end, struct mm_walk *walk)
@@ -451,19 +454,17 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
__split_huge_pmd(walk->vma, pmd, addr, false, NULL);
+ ret = 2;
goto out;
}
- if (!queue_pages_required(page, qp)) {
- ret = 1;
+ if (!queue_pages_required(page, qp))
goto unlock;
- }
- ret = 1;
flags = qp->flags;
/* go to thp migration */
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
if (!vma_migratable(walk->vma)) {
- ret = -EIO;
+ ret = 1;
goto unlock;
}
@@ -479,6 +480,13 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
/*
* Scan through pages checking if pages follow certain conditions,
* and move them to the pagelist if they do.
+ *
+ * queue_pages_pte_range() has three possible return values:
+ * 0 - pages are placed on the right node or queued successfully.
+ * 1 - there is unmovable page, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * -EIO - only MPOL_MF_STRICT was specified and an existing page was already
+ * on a node that does not follow the policy.
*/
static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
@@ -488,17 +496,17 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
struct queue_pages *qp = walk->private;
unsigned long flags = qp->flags;
int ret;
+ bool has_unmovable = false;
pte_t *pte;
spinlock_t *ptl;
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
ret = queue_pages_pmd(pmd, ptl, addr, end, walk);
- if (ret > 0)
- return 0;
- else if (ret < 0)
+ if (ret != 2)
return ret;
}
+ /* THP was split, fall through to pte walk */
if (pmd_trans_unstable(pmd))
return 0;
@@ -519,14 +527,21 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
if (!queue_pages_required(page, qp))
continue;
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
- if (!vma_migratable(vma))
+ /* MPOL_MF_STRICT must be specified if we get here */
+ if (!vma_migratable(vma)) {
+ has_unmovable = true;
break;
+ }
migrate_page_add(page, qp->pagelist, flags);
} else
break;
}
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
+
+ if (has_unmovable)
+ return 1;
+
return addr != end ? -EIO : 0;
}
@@ -639,7 +654,13 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
*
* If pages found in a given range are on a set of nodes (determined by
* @nodes and @flags,) it's isolated and queued to the pagelist which is
- * passed via @private.)
+ * passed via @private.
+ *
+ * queue_pages_range() has three possible return values:
+ * 1 - there is unmovable page, but MPOL_MF_MOVE* & MPOL_MF_STRICT were
+ * specified.
+ * 0 - queue pages successfully or no misplaced page.
+ * -EIO - there is misplaced page and only MPOL_MF_STRICT was specified.
*/
static int
queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
@@ -1182,6 +1203,7 @@ static long do_mbind(unsigned long start, unsigned long len,
struct mempolicy *new;
unsigned long end;
int err;
+ int ret;
LIST_HEAD(pagelist);
if (flags & ~(unsigned long)MPOL_MF_VALID)
@@ -1243,10 +1265,15 @@ static long do_mbind(unsigned long start, unsigned long len,
if (err)
goto mpol_out;
- err = queue_pages_range(mm, start, end, nmask,
+ ret = queue_pages_range(mm, start, end, nmask,
flags | MPOL_MF_INVERT, &pagelist);
- if (!err)
- err = mbind_range(mm, start, end, new);
+
+ if (ret < 0) {
+ err = -EIO;
+ goto up_out;
+ }
+
+ err = mbind_range(mm, start, end, new);
if (!err) {
int nr_failed = 0;
@@ -1259,13 +1286,14 @@ static long do_mbind(unsigned long start, unsigned long len,
putback_movable_pages(&pagelist);
}
- if (nr_failed && (flags & MPOL_MF_STRICT))
+ if ((ret > 0) || (nr_failed && (flags & MPOL_MF_STRICT)))
err = -EIO;
} else
putback_movable_pages(&pagelist);
+up_out:
up_write(&mm->mmap_sem);
- mpol_out:
+mpol_out:
mpol_put(new);
return err;
}
The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 1de13ee59225dfc98d483f8cce7d83f97c0b31de Mon Sep 17 00:00:00 2001
From: Ralph Campbell <rcampbell(a)nvidia.com>
Date: Tue, 13 Aug 2019 15:37:11 -0700
Subject: [PATCH] mm/hmm: fix bad subpage pointer in try_to_unmap_one
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
When migrating an anonymous private page to a ZONE_DEVICE private page,
the source page->mapping and page->index fields are copied to the
destination ZONE_DEVICE struct page and the page_mapcount() is
increased. This is so rmap_walk() can be used to unmap and migrate the
page back to system memory.
However, try_to_unmap_one() computes the subpage pointer from a swap pte
which computes an invalid page pointer and a kernel panic results such
as:
BUG: unable to handle page fault for address: ffffea1fffffffc8
Currently, only single pages can be migrated to device private memory so
no subpage computation is needed and it can be set to "page".
[rcampbell(a)nvidia.com: add comment]
Link: http://lkml.kernel.org/r/20190724232700.23327-4-rcampbell@nvidia.com
Link: http://lkml.kernel.org/r/20190719192955.30462-4-rcampbell@nvidia.com
Fixes: a5430dda8a3a1c ("mm/migrate: support un-addressable ZONE_DEVICE page in migration")
Signed-off-by: Ralph Campbell <rcampbell(a)nvidia.com>
Cc: "Jérôme Glisse" <jglisse(a)redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov(a)linux.intel.com>
Cc: Mike Kravetz <mike.kravetz(a)oracle.com>
Cc: Christoph Hellwig <hch(a)lst.de>
Cc: Jason Gunthorpe <jgg(a)mellanox.com>
Cc: John Hubbard <jhubbard(a)nvidia.com>
Cc: Andrea Arcangeli <aarcange(a)redhat.com>
Cc: Andrey Ryabinin <aryabinin(a)virtuozzo.com>
Cc: Christoph Lameter <cl(a)linux.com>
Cc: Dan Williams <dan.j.williams(a)intel.com>
Cc: Dave Hansen <dave.hansen(a)linux.intel.com>
Cc: Ira Weiny <ira.weiny(a)intel.com>
Cc: Jan Kara <jack(a)suse.cz>
Cc: Lai Jiangshan <jiangshanlai(a)gmail.com>
Cc: Logan Gunthorpe <logang(a)deltatee.com>
Cc: Martin Schwidefsky <schwidefsky(a)de.ibm.com>
Cc: Matthew Wilcox <willy(a)infradead.org>
Cc: Mel Gorman <mgorman(a)techsingularity.net>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Pekka Enberg <penberg(a)kernel.org>
Cc: Randy Dunlap <rdunlap(a)infradead.org>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index e5dfe2ae6b0d..003377e24232 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1475,7 +1475,15 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
/*
* No need to invalidate here it will synchronize on
* against the special swap migration pte.
+ *
+ * The assignment to subpage above was computed from a
+ * swap PTE which results in an invalid pointer.
+ * Since only PAGE_SIZE pages can currently be
+ * migrated, just set it to page. This will need to be
+ * changed when hugepage migrations to device private
+ * memory are supported.
*/
+ subpage = page;
goto discard;
}