syzbot


KASAN: use-after-free Read in do_madvise
Status: fixed on 2020/10/01 18:55
Reported-by: syzbot+b90df26038d1d5d85c97@syzkaller.appspotmail.com
Fix commit: 7867fd7cc44e mm: madvise: fix vma user-after-free
First crash: 644d, last: 642d

Cause bisection: failed (bisect log)

Sample crash report:
==================================================================
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 ffff8880a7e5eda8 by task syz-executor.0/13352

CPU: 1 PID: 13352 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:00007f775f6bac78 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: 00007ffc20ee540f R14: 00007f775f6bb9c0 R15: 000000000118cfec

Allocated by task 13348:
 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 13348:
 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

The buggy address belongs to the object at ffff8880a7e5eda8
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 0 bytes inside of
 200-byte region [ffff8880a7e5eda8, ffff8880a7e5ee70)
The buggy address belongs to the page:
page:00000000b39fa1b6 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa7e5e
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000268f1c8 ffffea000263dd48 ffff8880aa06f500
raw: 0000000000000000 ffff8880a7e5e040 000000010000000f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a7e5ec80: fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a7e5ed00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>ffff8880a7e5ed80: fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8880a7e5ee00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8880a7e5ee80: fc fc fc fc fc fc 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (4):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce-root 2020/08/22 02:32 upstream cd02217a5d81 6436ce4b .config log report syz
ci-upstream-kasan-gce-selinux-root 2020/08/21 06:20 upstream da2968ff879b 1d75fe45 .config log report syz
ci-upstream-kasan-gce-smack-root 2020/08/21 05:28 upstream da2968ff879b 1d75fe45 .config log report syz
ci-upstream-linux-next-kasan-gce-root 2020/08/23 04:37 linux-next 494d311a82bb 1da71ab0 .config log report syz