syzbot


KASAN: slab-out-of-bounds Write in init_sb
Status: fixed on 2020/11/25 03:55
Reported-by: syzbot+855f4ee05e58c7af0033@syzkaller.appspotmail.com
Fix commit: 78734edd11cc gfs2: add validation checks for size of superblock
First crash: 610d, last: 576d

Fix bisection: fixed by (bisect log) :
commit 78734edd11ccd3e4f88db9021a4d9856396aeabc
Author: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Date: Wed Oct 14 16:31:09 2020 +0000

  gfs2: add validation checks for size of superblock


Sample crash report:
audit: type=1400 audit(1600723809.458:8): avc:  denied  { execmem } for  pid=6367 comm="syz-executor079" scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=process permissive=1
gfs2: fsid=loop0: Trying to join cluster "lock_nolock", "loop0"
gfs2: fsid=loop0: Now mounting FS...
==================================================================
BUG: KASAN: slab-out-of-bounds in gfs2_read_sb fs/gfs2/ops_fstype.c:332 [inline]
BUG: KASAN: slab-out-of-bounds in init_sb+0xc60/0xd80 fs/gfs2/ops_fstype.c:488
Write of size 8 at addr ffff888097541bd0 by task syz-executor079/6367

CPU: 0 PID: 6367 Comm: syz-executor079 Not tainted 4.14.198-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_store8_noabort+0x68/0x70 mm/kasan/report.c:435
 gfs2_read_sb fs/gfs2/ops_fstype.c:332 [inline]
 init_sb+0xc60/0xd80 fs/gfs2/ops_fstype.c:488
 fill_super+0x15b0/0x2310 fs/gfs2/ops_fstype.c:1139
 gfs2_mount+0x439/0x502 fs/gfs2/ops_fstype.c:1331
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2549 [inline]
 do_mount+0xe53/0x2a00 fs/namespace.c:2879
 SYSC_mount fs/namespace.c:3095 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3072
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x446dba
RSP: 002b:00007fffe6cdf848 EFLAGS: 00000293 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffe6cdf8a0 RCX: 0000000000446dba
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fffe6cdf860
RBP: 00007fffe6cdf860 R08: 00007fffe6cdf8a0 R09: 00007fff00000015
R10: 0000000002200000 R11: 0000000000000293 R12: 0000000000000001
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003

Allocated by task 6367:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x131/0x3d0 mm/slab.c:3618
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 init_sbd fs/gfs2/ops_fstype.c:71 [inline]
 fill_super+0xb7/0x2310 fs/gfs2/ops_fstype.c:1060
 gfs2_mount+0x439/0x502 fs/gfs2/ops_fstype.c:1331
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2549 [inline]
 do_mount+0xe53/0x2a00 fs/namespace.c:2879
 SYSC_mount fs/namespace.c:3095 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3072
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff888097540800
 which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 5072 bytes inside of
 8192-byte region [ffff888097540800, ffff888097542800)
The buggy address belongs to the page:
page:ffffea00025d5000 count:1 mapcount:0 mapping:ffff888097540800 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff888097540800 0000000000000000 0000000100000001
raw: ffffea00025def20 ffff88812fe51b48 ffff88812fe48080 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888097541a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888097541b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888097541b80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                 ^
 ffff888097541c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888097541c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/09/21 21:31 linux-4.14.y cbfa1702aaf6 9e1fa68e .config log report syz C
ci2-linux-4-14 2020/10/25 17:03 linux-4.14.y 5b7a52cd2eef a1839e81 .config log report info
ci2-linux-4-14 2020/10/01 19:31 linux-4.14.y cbfa1702aaf6 4103fce0 .config log report info