* mm: BUG in munlock_vma_pages_range @ 2016-11-15 4:47 Dmitry Vyukov 2016-11-15 13:27 ` Kirill A. Shutemov 0 siblings, 1 reply; 2+ messages in thread From: Dmitry Vyukov @ 2016-11-15 4:47 UTC (permalink / raw) To: Andrew Morton, Vlastimil Babka, Kirill A. Shutemov, linux-mm, LKML, Konstantin Khlebnikov, Andrey Ryabinin Cc: syzkaller Hello, The following program triggers BUG in munlock_vma_pages_range: // autogenerated by syzkaller (http://github.com/google/syzkaller) #include <sys/mman.h> int main() { mmap((void*)0x20105000ul, 0xc00000ul, 0x2ul, 0x2172ul, -1, 0); mremap((void*)0x201fd000ul, 0x4000ul, 0xc00000ul, 0x3ul, 0x203f0000ul); return 0; } page:ffffea0001847cc0 count:0 mapcount:1 mapping:dead000000000400 index:0x20400 compound_mapcount: 1 flags: 0x5fffc0000000000() page dumped because: VM_BUG_ON_PAGE(PageMlocked(page)) ------------[ cut here ]------------ kernel BUG at mm/mlock.c:460! invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Modules linked in: CPU: 2 PID: 6526 Comm: a.out Not tainted 4.9.0-rc5+ #28 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff8800681ca0c0 task.stack: ffff8800637f0000 RIP: 0010:[<ffffffff81965272>] [<ffffffff81965272>] munlock_vma_pages_range+0xcc2/0x1010 mm/mlock.c:460 RSP: 0018:ffff8800637f7178 EFLAGS: 00010292 RAX: 0000000000000000 RBX: ffffea0001847cc0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88006d016e08 RDI: ffffed000c6fee20 RBP: ffff8800637f7638 R08: 0000000000000001 R09: 0000000000000000 R10: dffffc0000000000 R11: 0000000000000001 R12: ffffea0001847ce0 R13: ffffea0001840000 R14: dffffc0000000000 R15: ffff8800637f7610 FS: 0000000000000000(0000) GS:ffff88006d000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004b2080 CR3: 0000000064f87000 CR4: 00000000000006e0 Stack: 0000000041b58ab3 ffffffff894cfa90 ffff8800637f74f0 ffff8800637f7578 0000000000000005 ffff88007fff8000 1ffff1000c6fee42 ffff8800637f74b0 0000000020400000 000000050c6fee41 ffffea000196c55c ffffed000c6feeaf Call Trace: [< inline >] munlock_vma_pages_all mm/internal.h:277 [<ffffffff8197261b>] exit_mmap+0x1bb/0x4e0 mm/mmap.c:2924 [< inline >] __mmput kernel/fork.c:866 [<ffffffff813f24ce>] mmput+0x20e/0x4c0 kernel/fork.c:888 [< inline >] exit_mm kernel/exit.c:512 [<ffffffff814119a0>] do_exit+0x960/0x2640 kernel/exit.c:815 [<ffffffff8141383e>] do_group_exit+0x14e/0x420 kernel/exit.c:931 [< inline >] SYSC_exit_group kernel/exit.c:942 [<ffffffff81413b32>] SyS_exit_group+0x22/0x30 kernel/exit.c:940 [<ffffffff88143885>] entry_SYSCALL_64_fastpath+0x23/0xc6 arch/x86/entry/entry_64.S:209 Code: 0b e8 53 2e d8 ff 48 c7 c6 c0 32 31 88 48 89 df e8 54 2e fd ff 0f 0b e8 3d 2e d8 ff 48 c7 c6 80 35 31 88 48 89 df e8 3e 2e fd ff <0f> 0b 48 89 85 a8 fb ff ff e8 20 2e d8 ff 48 8b 85 a8 fb ff ff RIP [<ffffffff81965272>] munlock_vma_pages_range+0xcc2/0x1010 mm/mlock.c:460 RSP <ffff8800637f7178> ---[ end trace 694dc6462f524cf9 ]--- Fixing recursive fault but reboot is needed! On commit a25f0944ba9b1d8a6813fd6f1a86f1bd59ac25a6 (Nov 13). ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: mm: BUG in munlock_vma_pages_range 2016-11-15 4:47 mm: BUG in munlock_vma_pages_range Dmitry Vyukov @ 2016-11-15 13:27 ` Kirill A. Shutemov 0 siblings, 0 replies; 2+ messages in thread From: Kirill A. Shutemov @ 2016-11-15 13:27 UTC (permalink / raw) To: Dmitry Vyukov Cc: Andrew Morton, Vlastimil Babka, linux-mm, LKML, Konstantin Khlebnikov, Andrey Ryabinin, syzkaller On Tue, Nov 15, 2016 at 05:47:26AM +0100, Dmitry Vyukov wrote: > Hello, > > The following program triggers BUG in munlock_vma_pages_range: > > // autogenerated by syzkaller (http://github.com/google/syzkaller) > #include <sys/mman.h> > > int main() > { > mmap((void*)0x20105000ul, 0xc00000ul, 0x2ul, 0x2172ul, -1, 0); > mremap((void*)0x201fd000ul, 0x4000ul, 0xc00000ul, 0x3ul, 0x203f0000ul); > return 0; > } > > > page:ffffea0001847cc0 count:0 mapcount:1 mapping:dead000000000400 > index:0x20400 compound_mapcount: 1 > flags: 0x5fffc0000000000() > page dumped because: VM_BUG_ON_PAGE(PageMlocked(page)) Ughh.. mlock() again. This should fix the issue: >From cc6bc279ca713a19288610c31f8256dc885c5d7e Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Date: Tue, 15 Nov 2016 16:11:12 +0300 Subject: [PATCH] thp: fix corner case of munlock() of PTE-mapped THPs The following program triggers BUG() in munlock_vma_pages_range(): // autogenerated by syzkaller (http://github.com/google/syzkaller) #include <sys/mman.h> int main() { mmap((void*)0x20105000ul, 0xc00000ul, 0x2ul, 0x2172ul, -1, 0); mremap((void*)0x201fd000ul, 0x4000ul, 0xc00000ul, 0x3ul, 0x203f0000ul); return 0; } The test-case construct the situation when munlock_vma_pages_range() finds PTE-mapped THP-head in the middle of page table and, by mistake, skips HPAGE_PMD_NR pages after that. As result, on the next iteration it hits the middle of PMD-mapped THP and gets upset seeing mlocked tail page. The solution is only skip HPAGE_PMD_NR pages if the THP was mlocked during munlock_vma_page(). It would guarantee that the page is PMD-mapped as we never mlock PTE-mapeed THPs. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Fixes: e90309c9f772 ("thp: allow mlocked THP again") Cc: stable@vger.kernel.org # v4.5+ --- mm/mlock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index 145a4258ddbc..cdbed8aaa426 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -190,10 +190,13 @@ unsigned int munlock_vma_page(struct page *page) */ spin_lock_irq(zone_lru_lock(zone)); - nr_pages = hpage_nr_pages(page); - if (!TestClearPageMlocked(page)) + if (!TestClearPageMlocked(page)) { + /* Potentially, PTE-mapped THP: do not skip the rest PTEs */ + nr_pages = 1; goto unlock_out; + } + nr_pages = hpage_nr_pages(page); __mod_zone_page_state(zone, NR_MLOCK, -nr_pages); if (__munlock_isolate_lru_page(page, true)) { -- Kirill A. Shutemov ^ permalink raw reply related [flat|nested] 2+ messages in thread
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