Re: [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls

On 6/19/19 9:55 AM, Khalid Aziz wrote:

On 6/12/19 5:43 AM, Andrey Konovalov wrote:

...

This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments.

This patch allows tagged pointers to be passed to the following memory syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect, mremap, msync, munlock, move_pages.

The mmap and mremap syscalls do not currently accept tagged addresses. Architectures may interpret the tag as a background colour for the corresponding vma.

Reviewed-by: Catalin Marinas catalin.marinas@arm.com Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: Andrey Konovalov andreyknvl@google.com

---

Reviewed-by: Khalid Aziz khalid.aziz@oracle.com

I would also recommend updating commit log for all the patches in this series that are changing files under mm/ as opposed to arch/arm64 to not reference arm64 kernel ABI since the change applies to every architecture. So something along the lines of "This patch is part of a series that extends kernel ABI to allow......."

-- Khalid

...

mm/madvise.c | 2 ++ mm/mempolicy.c | 3 +++ mm/migrate.c | 2 +- mm/mincore.c | 2 ++ mm/mlock.c | 4 ++++ mm/mprotect.c | 2 ++ mm/mremap.c | 7 +++++++ mm/msync.c | 2 ++ 8 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c index 628022e674a7..39b82f8a698f 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -810,6 +810,8 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) size_t len; struct blk_plug plug;

• start = untagged_addr(start);
• if (!madvise_behavior_valid(behavior)) return error;

diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 01600d80ae01..78e0a88b2680 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1360,6 +1360,7 @@ static long kernel_mbind(unsigned long start, unsigned long len, int err; unsigned short mode_flags;

• start = untagged_addr(start); mode_flags = mode & MPOL_MODE_FLAGS; mode &= ~MPOL_MODE_FLAGS; if (mode >= MPOL_MAX)

@@ -1517,6 +1518,8 @@ static int kernel_get_mempolicy(int __user *policy, int uninitialized_var(pval); nodemask_t nodes;

• addr = untagged_addr(addr);
• if (nmask != NULL && maxnode < nr_node_ids) return -EINVAL;

diff --git a/mm/migrate.c b/mm/migrate.c index f2ecc2855a12..d22c45cf36b2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1616,7 +1616,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, goto out_flush; if (get_user(node, nodes + i)) goto out_flush;

• addr = (unsigned long)p;
  

• addr = (unsigned long)untagged_addr(p);
  

err = -ENODEV; if (node < 0 || node >= MAX_NUMNODES) diff --git a/mm/mincore.c b/mm/mincore.c index c3f058bd0faf..64c322ed845c 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -249,6 +249,8 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, unsigned long pages; unsigned char *tmp;

• start = untagged_addr(start);
• /* Check the start address: needs to be page-aligned.. */ if (start & ~PAGE_MASK) return -EINVAL;fixup_user_fault

diff --git a/mm/mlock.c b/mm/mlock.c index 080f3b36415b..e82609eaa428 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -674,6 +674,8 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla unsigned long lock_limit; int error = -ENOMEM;

• start = untagged_addr(start);
• if (!can_do_mlock()) return -EPERM;

@@ -735,6 +737,8 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) { int ret;

• start = untagged_addr(start);
• len = PAGE_ALIGN(len + (offset_in_page(start))); start &= PAGE_MASK;

diff --git a/mm/mprotect.c b/mm/mprotect.c index bf38dfbbb4b4..19f981b733bc 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -465,6 +465,8 @@ static int do_mprotect_pkey(unsigned long start, size_t len, const bool rier = (current->personality & READ_IMPLIES_EXEC) && (prot & PROT_READ);

• start = untagged_addr(start);
• prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ return -EINVAL;

diff --git a/mm/mremap.c b/mm/mremap.c index fc241d23cd97..64c9a3b8be0a 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -606,6 +606,13 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, LIST_HEAD(uf_unmap_early); LIST_HEAD(uf_unmap);

• /*

• * Architectures may interpret the tag passed to mmap as a background
  

• * colour for the corresponding vma. For mremap we don't allow tagged
  

• * new_addr to preserve similar behaviour to mmap.
  

• */
  

• addr = untagged_addr(addr);
• if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) return ret;

diff --git a/mm/msync.c b/mm/msync.c index ef30a429623a..c3bd3e75f687 100644 --- a/mm/msync.c +++ b/mm/msync.c @@ -37,6 +37,8 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) int unmapped_error = 0; int error = -EINVAL;

• start = untagged_addr(start);
• if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) goto out; if (offset_in_page(start))