On Fri, Aug 21, 2020 at 10:06 AM syzbot <syzbot+b90df26038d1d5d85c97@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: da2968ff Merge tag 'pci-v5.9-fixes-1' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1339995a900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=a0437fdd630bee11 > dashboard link: https://syzkaller.appspot.com/bug?extid=b90df26038d1d5d85c97 > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1225d919900000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b90df26038d1d5d85c97@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in madvise_willneed mm/madvise.c:293 [inline] > BUG: KASAN: use-after-free in madvise_vma mm/madvise.c:942 [inline] > BUG: KASAN: use-after-free in do_madvise.part.0+0x1c8b/0x1cf0 mm/madvise.c:1145 > Read of size 8 at addr ffff8880a6163eb0 by task syz-executor.0/9996 > > CPU: 0 PID: 9996 Comm: syz-executor.0 Not tainted 5.9.0-rc1-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x18f/0x20d lib/dump_stack.c:118 > print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383 > __kasan_report mm/kasan/report.c:513 [inline] > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 > madvise_willneed mm/madvise.c:293 [inline] > madvise_vma mm/madvise.c:942 [inline] > do_madvise.part.0+0x1c8b/0x1cf0 mm/madvise.c:1145 > do_madvise mm/madvise.c:1169 [inline] > __do_sys_madvise mm/madvise.c:1171 [inline] > __se_sys_madvise mm/madvise.c:1169 [inline] > __x64_sys_madvise+0xd9/0x110 mm/madvise.c:1169 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x45d4d9 > Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f04f7464c78 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > RAX: ffffffffffffffda RBX: 0000000000020800 RCX: 000000000045d4d9 > RDX: 0000000000000003 RSI: 0000000000600003 RDI: 0000000020000000 > RBP: 000000000118d020 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec > R13: 00007ffc579cce7f R14: 00007f04f74659c0 R15: 000000000118cfec > > Allocated by task 9992: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track mm/kasan/common.c:56 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 > slab_post_alloc_hook mm/slab.h:518 [inline] > slab_alloc mm/slab.c:3312 [inline] > kmem_cache_alloc+0x138/0x3a0 mm/slab.c:3482 > vm_area_alloc+0x1c/0x110 kernel/fork.c:347 > mmap_region+0x8e5/0x1780 mm/mmap.c:1743 > do_mmap+0xcf9/0x11d0 mm/mmap.c:1545 > vm_mmap_pgoff+0x195/0x200 mm/util.c:506 > ksys_mmap_pgoff+0x43a/0x560 mm/mmap.c:1596 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Freed by task 9992: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 > kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 > __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 > __cache_free mm/slab.c:3418 [inline] > kmem_cache_free.part.0+0x67/0x1f0 mm/slab.c:3693 > remove_vma+0x132/0x170 mm/mmap.c:184 > remove_vma_list mm/mmap.c:2613 [inline] > __do_munmap+0x743/0x1170 mm/mmap.c:2869 > do_munmap mm/mmap.c:2877 [inline] > mmap_region+0x257/0x1780 mm/mmap.c:1716 > do_mmap+0xcf9/0x11d0 mm/mmap.c:1545 > vm_mmap_pgoff+0x195/0x200 mm/util.c:506 > ksys_mmap_pgoff+0x43a/0x560 mm/mmap.c:1596 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 It looks the vma is gone. The below patch should be able to fix it: diff --git a/mm/madvise.c b/mm/madvise.c index dd1d43cf026d..d4aa5f776543 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -289,9 +289,9 @@ static long madvise_willneed(struct vm_area_struct *vma, */ *prev = NULL; /* tell sys_madvise we drop mmap_lock */ get_file(file); - mmap_read_unlock(current->mm); offset = (loff_t)(start - vma->vm_start) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); + mmap_read_unlock(current->mm); vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED); fput(file); mmap_read_lock(current->mm); > > The buggy address belongs to the object at ffff8880a6163eb0 > which belongs to the cache vm_area_struct of size 200 > The buggy address is located 0 bytes inside of > 200-byte region [ffff8880a6163eb0, ffff8880a6163f78) > The buggy address belongs to the page: > page:00000000dc1e014c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa6163 > flags: 0xfffe0000000200(slab) > raw: 00fffe0000000200 ffffea0002494bc8 ffffea0002a5ad88 ffff8880aa06f500 > raw: 0000000000000000 ffff8880a6163040 000000010000000f 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8880a6163d80: fc fc fc fc fc 00 00 00 00 00 00 00 00 00 00 00 > ffff8880a6163e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc > >ffff8880a6163e80: fc fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb > ^ > ffff8880a6163f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc > ffff8880a6163f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ================================================================== > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > syzbot can test patches for this issue, for details see: > https://goo.gl/tpsmEJ#testing-patches
