Wed, 08 Jul 2020 23:43:19 -0700 > syzbot found the following crash on: > > HEAD commit: e44f65fd xen-netfront: remove redundant assignment to vari.. > git tree: net-next > console output: https://syzkaller.appspot.com/x/log.txt?x=15de54a7100000 > kernel config: https://syzkaller.appspot.com/x/.config?x=829871134ca5e230 > dashboard link: https://syzkaller.appspot.com/bug?extid=ed318e8b790ca72c5ad0 > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=113406a7100000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=175597d3100000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+ed318e8b790ca72c5ad0@xxxxxxxxxxxxxxxxxxxxxxxxx > > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > CPU: 1 PID: 1155 Comm: khugepaged Not tainted 5.8.0-rc2-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > RIP: 0010:anon_vma_lock_write include/linux/rmap.h:120 [inline] > RIP: 0010:collapse_huge_page mm/khugepaged.c:1110 [inline] > RIP: 0010:khugepaged_scan_pmd mm/khugepaged.c:1349 [inline] > RIP: 0010:khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline] > RIP: 0010:khugepaged_do_scan mm/khugepaged.c:2193 [inline] > RIP: 0010:khugepaged+0x3bba/0x5a10 mm/khugepaged.c:2238 > Code: 01 00 00 48 8d bb 88 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 fa 0f 00 00 48 8b 9b 88 00 00 00 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 0f 85 d4 0f 00 00 48 8b 3b 48 83 c7 08 e8 9f ff 30 > RSP: 0018:ffffc90004be7c80 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81a72d8b > RDX: ffff8880a69d8100 RSI: ffffffff81b7606b RDI: ffff88809f0577c0 > RBP: 0000000000000000 R08: 0000000000000000 R09: ffff8881ff213a7f > R10: 0000000000000080 R11: 0000000000000000 R12: ffffffff8aae6110 > R13: ffffc90004be7de0 R14: dffffc0000000000 R15: 0000000020000000 > FS: 0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 00000001fe0cf000 CR4: 00000000001406e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > kthread+0x3b5/0x4a0 kernel/kthread.c:291 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -435,7 +435,8 @@ static inline int khugepaged_test_exit(s } static bool hugepage_vma_check(struct vm_area_struct *vma, - unsigned long vm_flags) + unsigned long vm_flags, + bool anon) { if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || (vm_flags & VM_NOHUGEPAGE) || @@ -446,6 +447,8 @@ static bool hugepage_vma_check(struct vm (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_DENYWRITE))) { + if (anon) + return false; return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, HPAGE_PMD_NR); } @@ -499,7 +502,7 @@ int khugepaged_enter_vma_merge(struct vm * khugepaged does not yet work on special mappings. And * file-private shmem THP is not supported. */ - if (!hugepage_vma_check(vma, vm_flags)) + if (!hugepage_vma_check(vma, vm_flags, false)) return 0; hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; @@ -956,7 +959,7 @@ static int hugepage_vma_revalidate(struc hend = vma->vm_end & HPAGE_PMD_MASK; if (address < hstart || address + HPAGE_PMD_SIZE > hend) return SCAN_ADDRESS_RANGE; - if (!hugepage_vma_check(vma, vma->vm_flags)) + if (!hugepage_vma_check(vma, vma->vm_flags, true)) return SCAN_VMA_CHECK; return 0; } @@ -1426,7 +1429,7 @@ void collapse_pte_mapped_thp(struct mm_s * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() * will not fail the vma for missing VM_HUGEPAGE */ - if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) + if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE, false)) return; pmd = mm_find_pmd(mm, haddr); @@ -2071,7 +2074,7 @@ static unsigned int khugepaged_scan_mm_s progress++; break; } - if (!hugepage_vma_check(vma, vma->vm_flags)) { + if (!hugepage_vma_check(vma, vma->vm_flags, false)) { skip: progress++; continue;
