Linux-stable-mirror December 2022

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[merged mm-stable] mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries.patch removed from -mm tree

by Andrew Morton

The quilt patch titled Subject: mm, compaction: fix fast_isolate_around() to stay within boundaries has been removed from the -mm tree. Its filename was mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: NARIBAYASHI Akira <a.naribayashi(a)fujitsu.com> Subject: mm, compaction: fix fast_isolate_around() to stay within boundaries Date: Wed, 26 Oct 2022 20:24:38 +0900 Depending on the memory configuration, isolate_freepages_block() may scan pages out of the target range and causes panic. Panic can occur on systems with multiple zones in a single pageblock. The reason it is rare is that it only happens in special configurations. Depending on how many similar systems there are, it may be a good idea to fix this problem for older kernels as well. The problem is that pfn as argument of fast_isolate_around() could be out of the target range. Therefore we should consider the case where pfn < start_pfn, and also the case where end_pfn < pfn. This problem should have been addressd by the commit 6e2b7044c199 ("mm, compaction: make fast_isolate_freepages() stay within zone") but there was an oversight. Case1: pfn < start_pfn <at memory compaction for node Y> | node X's zone | node Y's zone +-----------------+------------------------------... pageblock ^ ^ ^ +-----------+-----------+-----------+-----------+... ^ ^ ^ ^ ^ end_pfn ^ start_pfn = cc->zone->zone_start_pfn pfn <---------> scanned range by "Scan After" Case2: end_pfn < pfn <at memory compaction for node X> | node X's zone | node Y's zone +-----------------+------------------------------... pageblock ^ ^ ^ +-----------+-----------+-----------+-----------+... ^ ^ ^ ^ ^ pfn ^ end_pfn start_pfn <---------> scanned range by "Scan Before" It seems that there is no good reason to skip nr_isolated pages just after given pfn. So let perform simple scan from start to end instead of dividing the scan into "Before" and "After". Link: https://lkml.kernel.org/r/20221026112438.236336-1-a.naribayashi@fujitsu.com Fixes: 6e2b7044c199 ("mm, compaction: make fast_isolate_freepages() stay within zone"). Signed-off-by: NARIBAYASHI Akira <a.naribayashi(a)fujitsu.com> Cc: David Rientjes <rientjes(a)google.com> Cc: Mel Gorman <mgorman(a)techsingularity.net> Cc: Vlastimil Babka <vbabka(a)suse.cz> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/compaction.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-) --- a/mm/compaction.c~mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries +++ a/mm/compaction.c @@ -1344,7 +1344,7 @@ move_freelist_tail(struct list_head *fre } static void -fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated) +fast_isolate_around(struct compact_control *cc, unsigned long pfn) { unsigned long start_pfn, end_pfn; struct page *page; @@ -1365,21 +1365,13 @@ fast_isolate_around(struct compact_contr if (!page) return; - /* Scan before */ - if (start_pfn != pfn) { - isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false); - if (cc->nr_freepages >= cc->nr_migratepages) - return; - } - - /* Scan after */ - start_pfn = pfn + nr_isolated; - if (start_pfn < end_pfn) - isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); + isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); /* Skip this pageblock in the future as it's full or nearly full */ if (cc->nr_freepages < cc->nr_migratepages) set_pageblock_skip(page); + + return; } /* Search orders in round-robin fashion */ @@ -1556,7 +1548,7 @@ fast_isolate_freepages(struct compact_co return cc->free_pfn; low_pfn = page_to_pfn(page); - fast_isolate_around(cc, low_pfn, nr_isolated); + fast_isolate_around(cc, low_pfn); return low_pfn; } _ Patches currently in -mm which might be from a.naribayashi(a)fujitsu.com are

2 years

[merged mm-stable] mm-gup-disallow-foll_forcefoll_write-on-hugetlb-mappings.patch removed from -mm tree

by Andrew Morton

The quilt patch titled Subject: mm/gup: disallow FOLL_FORCE|FOLL_WRITE on hugetlb mappings has been removed from the -mm tree. Its filename was mm-gup-disallow-foll_forcefoll_write-on-hugetlb-mappings.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: David Hildenbrand <david(a)redhat.com> Subject: mm/gup: disallow FOLL_FORCE|FOLL_WRITE on hugetlb mappings Date: Mon, 31 Oct 2022 16:25:24 +0100 hugetlb does not support fake write-faults (write faults without write permissions). However, we are currently able to trigger a FAULT_FLAG_WRITE fault on a VMA without VM_WRITE. If we'd ever want to support FOLL_FORCE|FOLL_WRITE, we'd have to teach hugetlb to: (1) Leave the page mapped R/O after the fake write-fault, like maybe_mkwrite() does. (2) Allow writing to an exclusive anon page that's mapped R/O when FOLL_FORCE is set, like can_follow_write_pte(). E.g., __follow_hugetlb_must_fault() needs adjustment. For now, it's not clear if that added complexity is really required. History tolds us that FOLL_FORCE is dangerous and that we better limit its use to a bare minimum. -------------------------------------------------------------------------- #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <errno.h> #include <stdint.h> #include <sys/mman.h> #include <linux/mman.h> int main(int argc, char **argv) { char *map; int mem_fd; map = mmap(NULL, 2 * 1024 * 1024u, PROT_READ, MAP_PRIVATE|MAP_ANON|MAP_HUGETLB|MAP_HUGE_2MB, -1, 0); if (map == MAP_FAILED) { fprintf(stderr, "mmap() failed: %d\n", errno); return 1; } mem_fd = open("/proc/self/mem", O_RDWR); if (mem_fd < 0) { fprintf(stderr, "open(/proc/self/mem) failed: %d\n", errno); return 1; } if (pwrite(mem_fd, "0", 1, (uintptr_t) map) == 1) { fprintf(stderr, "write() succeeded, which is unexpected\n"); return 1; } printf("write() failed as expected: %d\n", errno); return 0; } -------------------------------------------------------------------------- Fortunately, we have a sanity check in hugetlb_wp() in place ever since commit 1d8d14641fd9 ("mm/hugetlb: support write-faults in shared mappings"), that bails out instead of silently mapping a page writable in a !PROT_WRITE VMA. Consequently, above reproducer triggers a warning, similar to the one reported by szsbot: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 3612 at mm/hugetlb.c:5313 hugetlb_wp+0x20a/0x1af0 mm/hugetlb.c:5313 Modules linked in: CPU: 1 PID: 3612 Comm: syz-executor250 Not tainted 6.1.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 RIP: 0010:hugetlb_wp+0x20a/0x1af0 mm/hugetlb.c:5313 Code: ea 03 80 3c 02 00 0f 85 31 14 00 00 49 8b 5f 20 31 ff 48 89 dd 83 e5 02 48 89 ee e8 70 ab b7 ff 48 85 ed 75 5b e8 76 ae b7 ff <0f> 0b 41 bd 40 00 00 00 e8 69 ae b7 ff 48 b8 00 00 00 00 00 fc ff RSP: 0018:ffffc90003caf620 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000008640070 RCX: 0000000000000000 RDX: ffff88807b963a80 RSI: ffffffff81c4ed2a RDI: 0000000000000007 RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000 R10: 0000000000000000 R11: 000000000008c07e R12: ffff888023805800 R13: 0000000000000000 R14: ffffffff91217f38 R15: ffff88801d4b0360 FS: 0000555555bba300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fff7a47a1b8 CR3: 000000002378d000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> hugetlb_no_page mm/hugetlb.c:5755 [inline] hugetlb_fault+0x19cc/0x2060 mm/hugetlb.c:5874 follow_hugetlb_page+0x3f3/0x1850 mm/hugetlb.c:6301 __get_user_pages+0x2cb/0xf10 mm/gup.c:1202 __get_user_pages_locked mm/gup.c:1434 [inline] __get_user_pages_remote+0x18f/0x830 mm/gup.c:2187 get_user_pages_remote+0x84/0xc0 mm/gup.c:2260 __access_remote_vm+0x287/0x6b0 mm/memory.c:5517 ptrace_access_vm+0x181/0x1d0 kernel/ptrace.c:61 generic_ptrace_pokedata kernel/ptrace.c:1323 [inline] ptrace_request+0xb46/0x10c0 kernel/ptrace.c:1046 arch_ptrace+0x36/0x510 arch/x86/kernel/ptrace.c:828 __do_sys_ptrace kernel/ptrace.c:1296 [inline] __se_sys_ptrace kernel/ptrace.c:1269 [inline] __x64_sys_ptrace+0x178/0x2a0 kernel/ptrace.c:1269 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] So let's silence that warning by teaching GUP code that FOLL_FORCE -- so far -- does not apply to hugetlb. Note that FOLL_FORCE for read-access seems to be working as expected. The assumption is that this has been broken forever, only ever since above commit, we actually detect the wrong handling and WARN_ON_ONCE(). I assume this has been broken at least since 2014, when mm/gup.c came to life. I failed to come up with a suitable Fixes tag quickly. Link: https://lkml.kernel.org/r/20221031152524.173644-1-david@redhat.com Fixes: 1d8d14641fd9 ("mm/hugetlb: support write-faults in shared mappings") Signed-off-by: David Hildenbrand <david(a)redhat.com> Reported-by: <syzbot+f0b97304ef90f0d0b1dc(a)syzkaller.appspotmail.com> Cc: Mike Kravetz <mike.kravetz(a)oracle.com> Cc: Peter Xu <peterx(a)redhat.com> Cc: John Hubbard <jhubbard(a)nvidia.com> Cc: Jason Gunthorpe <jgg(a)nvidia.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/gup.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/gup.c~mm-gup-disallow-foll_forcefoll_write-on-hugetlb-mappings +++ a/mm/gup.c @@ -1009,6 +1009,9 @@ static int check_vma_flags(struct vm_are if (!(vm_flags & VM_WRITE)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; + /* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */ + if (is_vm_hugetlb_page(vma)) + return -EFAULT; /* * We used to let the write,force case do COW in a * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could _ Patches currently in -mm which might be from david(a)redhat.com are selftests-vm-add-ksm-unmerge-tests.patch mm-pagewalk-dont-trigger-test_walk-in-walk_page_vma.patch selftests-vm-add-test-to-measure-madv_unmergeable-performance.patch mm-ksm-simplify-break_ksm-to-not-rely-on-vm_fault_write.patch mm-remove-vm_fault_write.patch mm-ksm-fix-ksm-cow-breaking-with-userfaultfd-wp-via-fault_flag_unshare.patch mm-pagewalk-add-walk_page_range_vma.patch mm-ksm-convert-break_ksm-to-use-walk_page_range_vma.patch mm-gup-remove-foll_migration.patch

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Linux-stable-mirror December 2022