KASAN: use-after-free Read in path_init (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4e78c578 Add linux-next specific files for 20201030
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=110d0c92500000
kernel config: https://syzkaller.appspot.com/x/.config?x=83318758268dc331
dashboard link: https://syzkaller.appspot.com/bug?extid=3e565bbd2673747f90c2
compiler: gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3e565b...@syzkaller.appspotmail.com

MINIX-fs: mounting unchecked file system, running fsck is recommended
MINIX-fs: deleted inode referenced: 6
==================================================================
BUG: KASAN: use-after-free in path_init+0x14ba/0x17d0 fs/namei.c:2208
Read of size 8 at addr ffff8880633cc400 by task syz-executor.3/14486

CPU: 1 PID: 14486 Comm: syz-executor.3 Not tainted 5.10.0-rc1-next-20201030-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+0x107/0x163 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
path_init+0x14ba/0x17d0 fs/namei.c:2208
path_parentat+0x22/0x1b0 fs/namei.c:2385
filename_parentat+0x188/0x560 fs/namei.c:2408
do_renameat2+0x16e/0xc00 fs/namei.c:4375
__do_sys_renameat fs/namei.c:4501 [inline]
__se_sys_renameat fs/namei.c:4498 [inline]
__x64_sys_renameat+0xbf/0xf0 fs/namei.c:4498
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45deb9
Code: 0d 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbef8029c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000108
RAX: ffffffffffffffda RBX: 0000000000027340 RCX: 000000000045deb9
RDX: 0000000000000006 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 000000000118bf68 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000200017c0 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe203745cf R14: 00007fbef802a9c0 R15: 000000000118bf2c

Allocated by task 14486:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
slab_post_alloc_hook mm/slab.h:506 [inline]
slab_alloc_node mm/slub.c:2889 [inline]
slab_alloc mm/slub.c:2897 [inline]
kmem_cache_alloc+0x122/0x460 mm/slub.c:2902
getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
getname_flags+0x9a/0xe0 include/linux/audit.h:319
getname fs/namei.c:209 [inline]
__do_sys_renameat fs/namei.c:4501 [inline]
__se_sys_renameat fs/namei.c:4498 [inline]
__x64_sys_renameat+0xad/0xf0 fs/namei.c:4498
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 14486:
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+0x102/0x140 mm/kasan/common.c:422
slab_free_hook mm/slub.c:1544 [inline]
slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1577
slab_free mm/slub.c:3140 [inline]
kmem_cache_free+0x82/0x350 mm/slub.c:3156
putname+0xe1/0x120 fs/namei.c:259
do_renameat2+0x3e6/0xc00 fs/namei.c:4481
__do_sys_renameat fs/namei.c:4501 [inline]
__se_sys_renameat fs/namei.c:4498 [inline]
__x64_sys_renameat+0xbf/0xf0 fs/namei.c:4498
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 ffff8880633cc400
which belongs to the cache names_cache of size 4096
The buggy address is located 0 bytes inside of
4096-byte region [ffff8880633cc400, ffff8880633cd400)
The buggy address belongs to the page:
page:00000000f2c066e0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x633c8
head:00000000f2c066e0 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff8880101c1280
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880633cc300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880633cc380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880633cc400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880633cc480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880633cc500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.