KASAN: use-after-free Read in xlog_alloc_log

From: syzbot
Date: Thu Jun 27 2019 - 02:50:29 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 1dd45f17 Add linux-next specific files for 20190626
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=172479e9a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c1222640552e42a5
dashboard link: https://syzkaller.appspot.com/bug?extid=b75afdbe271a0d7ac4f6
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+b75afdbe271a0d7ac4f6@xxxxxxxxxxxxxxxxxxxxxxxxx

XFS (loop5): Mounting V4 Filesystem
==================================================================
BUG: KASAN: use-after-free in xlog_alloc_log+0x1266/0x1380 fs/xfs/xfs_log.c:1478
Read of size 8 at addr ffff8880693e2990 by task syz-executor.5/12241

CPU: 1 PID: 12241 Comm: syz-executor.5 Not tainted 5.2.0-rc6-next-20190626 #23
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+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
__kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
kasan_report+0x12/0x17 mm/kasan/common.c:614
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
xlog_alloc_log+0x1266/0x1380 fs/xfs/xfs_log.c:1478
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:580
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:815
xfs_fs_fill_super+0xca6/0x16c0 fs/xfs/xfs_super.c:1740
mount_bdev+0x304/0x3c0 fs/super.c:1346
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1814
legacy_get_tree+0x108/0x220 fs/fs_context.c:661
vfs_get_tree+0x8e/0x390 fs/super.c:1476
do_new_mount fs/namespace.c:2791 [inline]
do_mount+0x138c/0x1c00 fs/namespace.c:3111
ksys_mount+0xdb/0x150 fs/namespace.c:3320
__do_sys_mount fs/namespace.c:3334 [inline]
__se_sys_mount fs/namespace.c:3331 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3331
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45bf6a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d 8d 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 7a 8d fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fac99605a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fac99605b40 RCX: 000000000045bf6a
RDX: 00007fac99605ae0 RSI: 0000000020000000 RDI: 00007fac99605b00
RBP: 0000000000000001 R08: 00007fac99605b40 R09: 00007fac99605ae0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000004
R13: 00000000004c858e R14: 00000000004df0e0 R15: 00000000ffffffff

Allocated by task 12241:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_kmalloc mm/kasan/common.c:489 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x163/0x770 mm/slab.c:3665
kmalloc include/linux/slab.h:556 [inline]
kmem_alloc+0xd2/0x200 fs/xfs/kmem.c:24
kmem_zalloc fs/xfs/kmem.h:73 [inline]
xlog_alloc_log+0xbf4/0x1380 fs/xfs/xfs_log.c:1420
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:580
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:815
xfs_fs_fill_super+0xca6/0x16c0 fs/xfs/xfs_super.c:1740
mount_bdev+0x304/0x3c0 fs/super.c:1346
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1814
legacy_get_tree+0x108/0x220 fs/fs_context.c:661
vfs_get_tree+0x8e/0x390 fs/super.c:1476
do_new_mount fs/namespace.c:2791 [inline]
do_mount+0x138c/0x1c00 fs/namespace.c:3111
ksys_mount+0xdb/0x150 fs/namespace.c:3320
__do_sys_mount fs/namespace.c:3334 [inline]
__se_sys_mount fs/namespace.c:3331 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3331
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 12241:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x2c0 mm/slab.c:3757
kvfree+0x61/0x70 mm/util.c:488
kmem_free fs/xfs/kmem.h:66 [inline]
xlog_alloc_log+0xea9/0x1380 fs/xfs/xfs_log.c:1480
xfs_log_mount+0xdc/0x780 fs/xfs/xfs_log.c:580
xfs_mountfs+0xdb9/0x1be0 fs/xfs/xfs_mount.c:815
xfs_fs_fill_super+0xca6/0x16c0 fs/xfs/xfs_super.c:1740
mount_bdev+0x304/0x3c0 fs/super.c:1346
xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1814
legacy_get_tree+0x108/0x220 fs/fs_context.c:661
vfs_get_tree+0x8e/0x390 fs/super.c:1476
do_new_mount fs/namespace.c:2791 [inline]
do_mount+0x138c/0x1c00 fs/namespace.c:3111
ksys_mount+0xdb/0x150 fs/namespace.c:3320
__do_sys_mount fs/namespace.c:3334 [inline]
__se_sys_mount fs/namespace.c:3331 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3331
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880693e2900
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 144 bytes inside of
1024-byte region [ffff8880693e2900, ffff8880693e2d00)
The buggy address belongs to the page:
page:ffffea0001a4f880 refcount:1 mapcount:0 mapping:ffff8880aa400c40 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00018ec788 ffffea0002473908 ffff8880aa400c40
raw: 0000000000000000 ffff8880693e2000 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880693e2880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880693e2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

ffff8880693e2980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff8880693e2a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880693e2a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Thomas Gleixner: "Re: [PATCH v3 6/7] x86/smpboot: introduce per-cpu variable for HT siblings"
Previous message: syzbot: "KASAN: use-after-free Write in xfrm_policy_flush"
Next in thread: Christoph Hellwig: "Re: KASAN: use-after-free Read in xlog_alloc_log"
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