KASAN: use-after-free Read in xlog_alloc_log (2)

syzbot
2019-11-30T07:19:10Z

Hello,

syzbot found the following crash on:

HEAD commit: 81b6b964 Merge branch 'master' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b27696e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=773597fe8d7cb41a
dashboard link: https://syzkaller.appspot.com/bug?extid=c732f8644185de340492
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c732f8644185de340492@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in xlog_alloc_log+0x1398/0x14b0
fs/xfs/xfs_log.c:1495
Read of size 8 at addr ffff888068139890 by task syz-executor.3/32544

CPU: 0 PID: 32544 Comm: syz-executor.3 Not tainted 5.4.0-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/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:634
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
xlog_alloc_log+0x1398/0x14b0 fs/xfs/xfs_log.c:1495
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:599
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:811
xfs_fs_fill_super+0xd24/0x1750 fs/xfs/xfs_super.c:1732
mount_bdev+0x304/0x3c0 fs/super.c:1415
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1806
legacy_get_tree+0x108/0x220 fs/fs_context.c:647
vfs_get_tree+0x8e/0x300 fs/super.c:1545
do_new_mount fs/namespace.c:2822 [inline]
do_mount+0x135a/0x1b50 fs/namespace.c:3142
ksys_mount+0xdb/0x150 fs/namespace.c:3351
__do_sys_mount fs/namespace.c:3365 [inline]
__se_sys_mount fs/namespace.c:3362 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3362
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45d0ca
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 4d 8c 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 2a 8c fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f525b430a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f525b430b40 RCX: 000000000045d0ca
RDX: 00007f525b430ae0 RSI: 0000000020000100 RDI: 00007f525b430b00
RBP: 0000000000000001 R08: 00007f525b430b40 R09: 00007f525b430ae0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000004
R13: 00000000004ca258 R14: 00000000004e2870 R15: 00000000ffffffff

Allocated by task 32544:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc mm/kasan/common.c:510 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
__do_kmalloc mm/slab.c:3655 [inline]
__kmalloc+0x163/0x770 mm/slab.c:3664
kmalloc include/linux/slab.h:561 [inline]
kmem_alloc+0x15b/0x4d0 fs/xfs/kmem.c:21
kmem_zalloc fs/xfs/kmem.h:68 [inline]
xlog_alloc_log+0xcce/0x14b0 fs/xfs/xfs_log.c:1437
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:599
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:811
xfs_fs_fill_super+0xd24/0x1750 fs/xfs/xfs_super.c:1732
mount_bdev+0x304/0x3c0 fs/super.c:1415
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1806
legacy_get_tree+0x108/0x220 fs/fs_context.c:647
vfs_get_tree+0x8e/0x300 fs/super.c:1545
do_new_mount fs/namespace.c:2822 [inline]
do_mount+0x135a/0x1b50 fs/namespace.c:3142
ksys_mount+0xdb/0x150 fs/namespace.c:3351
__do_sys_mount fs/namespace.c:3365 [inline]
__se_sys_mount fs/namespace.c:3362 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3362
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 32544:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
kasan_set_free_info mm/kasan/common.c:332 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
__cache_free mm/slab.c:3425 [inline]
kfree+0x10a/0x2c0 mm/slab.c:3756
kvfree+0x61/0x70 mm/util.c:593
kmem_free fs/xfs/kmem.h:61 [inline]
xlog_alloc_log+0xeb5/0x14b0 fs/xfs/xfs_log.c:1497
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:599
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:811
xfs_fs_fill_super+0xd24/0x1750 fs/xfs/xfs_super.c:1732
mount_bdev+0x304/0x3c0 fs/super.c:1415
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1806
legacy_get_tree+0x108/0x220 fs/fs_context.c:647
vfs_get_tree+0x8e/0x300 fs/super.c:1545
do_new_mount fs/namespace.c:2822 [inline]
do_mount+0x135a/0x1b50 fs/namespace.c:3142
ksys_mount+0xdb/0x150 fs/namespace.c:3351
__do_sys_mount fs/namespace.c:3365 [inline]
__se_sys_mount fs/namespace.c:3362 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3362
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 ffff888068139800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 144 bytes inside of
1024-byte region [ffff888068139800, ffff888068139c00)
The buggy address belongs to the page:
page:ffffea0001a04e40 refcount:1 mapcount:0 mapping:ffff8880aa400c40
index:0x0
raw: 00fffe0000000200 ffffea0002728148 ffffea00015604c8 ffff8880aa400c40
raw: 0000000000000000 ffff888068139000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888068139780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888068139800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888068139880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888068139900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888068139980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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