KASAN: slab-out-of-bounds Read in suffix_kstrtoint

From: syzbot
Date: Thu Feb 06 2020 - 22:48:27 EST

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Hello,

syzbot found the following crash on:

HEAD commit: a0c61bf1 Add linux-next specific files for 20200206
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13925e6ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7d320d6d9afdaecd
dashboard link: https://syzkaller.appspot.com/bug?extid=c23efa0cc68e79d551fc
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1725bad9e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15ac3c5ee00000

The bug was bisected to:

commit 61dff92158775e70c0183f4f52c3a5a071dbc24b
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Tue Dec 17 19:15:04 2019 +0000

Pass consistent param->type to fs_parse()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11fa020de00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=13fa020de00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15fa020de00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c23efa0cc68e79d551fc@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 61dff9215877 ("Pass consistent param->type to fs_parse()")

==================================================================
BUG: KASAN: slab-out-of-bounds in suffix_kstrtoint.constprop.0+0x214/0x250 fs/xfs/xfs_super.c:1083
Read of size 1 at addr ffff8880a4b5b3ff by task syz-executor933/9793

CPU: 0 PID: 9793 Comm: syz-executor933 Not tainted 5.5.0-next-20200206-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+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:641
__asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132
suffix_kstrtoint.constprop.0+0x214/0x250 fs/xfs/xfs_super.c:1083
xfs_fc_parse_param+0x991/0xcd0 fs/xfs/xfs_super.c:1127
vfs_parse_fs_param+0x2b4/0x610 fs/fs_context.c:147
vfs_parse_fs_string+0x10a/0x170 fs/fs_context.c:191
generic_parse_monolithic+0x181/0x200 fs/fs_context.c:231
parse_monolithic_mount_data+0x69/0x90 fs/fs_context.c:679
do_new_mount fs/namespace.c:2818 [inline]
do_mount+0x1310/0x1b50 fs/namespace.c:3107
__do_sys_mount fs/namespace.c:3316 [inline]
__se_sys_mount fs/namespace.c:3293 [inline]
__x64_sys_mount+0x192/0x230 fs/namespace.c:3293
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446a8a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d ae fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 5a ae fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffc8d9430c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc8d9430d0 RCX: 0000000000446a8a
RDX: 00007ffc8d9430d0 RSI: 0000000020000080 RDI: 00007ffc8d9430f0
RBP: 0000000000000003 R08: 00007ffc8d943130 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffc8d943130
R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 9791:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x163/0x770 mm/slab.c:3665
kmalloc include/linux/slab.h:560 [inline]
kzalloc include/linux/slab.h:669 [inline]
tomoyo_encode2.part.0+0xf5/0x400 security/tomoyo/realpath.c:44
tomoyo_encode2 security/tomoyo/realpath.c:30 [inline]
tomoyo_encode+0x2b/0x50 security/tomoyo/realpath.c:79
tomoyo_realpath_from_path+0x19c/0x660 security/tomoyo/realpath.c:286
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x230/0x430 security/tomoyo/file.c:822
tomoyo_inode_getattr+0x1d/0x30 security/tomoyo/tomoyo.c:129
security_inode_getattr+0xf2/0x150 security/security.c:1254
vfs_getattr+0x25/0x70 fs/stat.c:117
vfs_statx_fd+0x71/0xc0 fs/stat.c:147
vfs_fstat include/linux/fs.h:3287 [inline]
__do_sys_newfstat+0x9b/0x120 fs/stat.c:388
__se_sys_newfstat fs/stat.c:385 [inline]
__x64_sys_newfstat+0x54/0x80 fs/stat.c:385
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9791:
save_stack+0x23/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x2c0 mm/slab.c:3757
tomoyo_path_perm+0x24e/0x430 security/tomoyo/file.c:842
tomoyo_inode_getattr+0x1d/0x30 security/tomoyo/tomoyo.c:129
security_inode_getattr+0xf2/0x150 security/security.c:1254
vfs_getattr+0x25/0x70 fs/stat.c:117
vfs_statx_fd+0x71/0xc0 fs/stat.c:147
vfs_fstat include/linux/fs.h:3287 [inline]
__do_sys_newfstat+0x9b/0x120 fs/stat.c:388
__se_sys_newfstat fs/stat.c:385 [inline]
__x64_sys_newfstat+0x54/0x80 fs/stat.c:385
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a4b5b3c0
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 31 bytes to the right of
32-byte region [ffff8880a4b5b3c0, ffff8880a4b5b3e0)
The buggy address belongs to the page:
page:ffffea000292d6c0 refcount:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff8880a4b5bfc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002a15908 ffffea00025c80c8 ffff8880aa4001c0
raw: ffff8880a4b5bfc1 ffff8880a4b5b000 0000000100000028 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a4b5b280: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8880a4b5b300: 00 03 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8880a4b5b380: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
^
ffff8880a4b5b400: 01 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
ffff8880a4b5b480: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

---
This bug 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@xxxxxxxxxxxxxxxxx

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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

Next message: Dave Chinner: "Re: [PATCH v12 1/2] fs: New zonefs file system"
Previous message: John Hubbard: "[PATCH v5 09/12] mm: dump_page(): better diagnostics for huge pinned pages"
Next in thread: Al Viro: "Re: KASAN: slab-out-of-bounds Read in suffix_kstrtoint"
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