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

Status: fixed on 2020/09/16 22:51
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+bbeb1c88016c7db4aa24@syzkaller.appspotmail.com
Fix commit: 24fb33d40d60 fix breakage in do_rmdir()
First crash: 1595d, last: 1589d
Cause bisection: introduced by (bisect log) :
commit e24ab0ef689de43649327f54cd1088f3dad25bb3
Author: Christoph Hellwig <hch@lst.de>
Date: Tue Jul 21 08:48:15 2020 +0000

  fs: push the getname from do_rmdir into the callers

Crash: kernel BUG at fs/namei.c:LINE! (log)
Repro: syz .config
  
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in path_init (2) 0 (2) 2020/08/12 21:28
[PATCH] Re: KASAN: use-after-free Read in path_init (2) 4 (4) 2020/08/12 17:23
▶ ▼ Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in path_init fs 1 2428d 2426d 0/28 auto-closed as invalid on 2019/02/22 10:09
upstream KASAN: use-after-free Read in path_init (3) fs 2 1511d 1506d 0/28 auto-closed as invalid on 2020/12/29 19:01

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in path_init+0x116b/0x13c0 fs/namei.c:2207
Read of size 8 at addr ffff8880a0508700 by task syz-executor159/6828

CPU: 1 PID: 6828 Comm: syz-executor159 Not tainted 5.8.0-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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 path_init+0x116b/0x13c0 fs/namei.c:2207
 path_parentat+0x22/0x1b0 fs/namei.c:2384
 filename_parentat+0x188/0x560 fs/namei.c:2407
 do_rmdir+0xa8/0x440 fs/namei.c:3732
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4403e9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff37be5c38 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 69662f7375622f2e RCX: 00000000004403e9
RDX: 00000000004403e9 RSI: 00000000004403e9 RDI: 0000000020000080
RBP: 2f31656c69662f2e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401bf0
R13: 0000000000401c80 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6828:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 slab_post_alloc_hook mm/slab.h:518 [inline]
 slab_alloc mm/slab.c:3312 [inline]
 kmem_cache_alloc+0x138/0x3a0 mm/slab.c:3482
 getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
 getname_flags include/linux/audit.h:320 [inline]
 getname fs/namei.c:209 [inline]
 __do_sys_rmdir fs/namei.c:3783 [inline]
 __se_sys_rmdir fs/namei.c:3781 [inline]
 __x64_sys_rmdir+0xb1/0x100 fs/namei.c:3781
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6828:
 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+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kmem_cache_free.part.0+0x67/0x1f0 mm/slab.c:3693
 putname+0xe1/0x120 fs/namei.c:259
 do_rmdir+0x145/0x440 fs/namei.c:3773
 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 ffff8880a0508700
 which belongs to the cache names_cache of size 4096
The buggy address is located 0 bytes inside of
 4096-byte region [ffff8880a0508700, ffff8880a0509700)
The buggy address belongs to the page:
page:00000000585345a4 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa0508
head:00000000585345a4 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0002832d88 ffff8880aa247150 ffff8880aa241900
raw: 0000000000000000 ffff8880a0508700 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a0508600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a0508680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a0508700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880a0508780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a0508800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (29):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/08/12 21:35 upstream fb893de323e2 bc15f7db .config console log report syz C ci-upstream-kasan-gce-selinux-root
2020/08/12 21:30 upstream fb893de323e2 bc15f7db .config console log report syz C ci-upstream-kasan-gce-smack-root
2020/08/12 21:27 upstream fb893de323e2 bc15f7db .config console log report syz C ci-upstream-kasan-gce-root
2020/08/12 21:34 linux-next bc09acc9f224 bc15f7db .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2020/08/13 14:02 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/08/13 13:33 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/08/13 13:03 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/08/12 23:45 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/12 23:26 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/12 23:07 upstream fb893de323e2 bc15f7db .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/11 06:51 upstream fc80c51fd4b2 7adc7b65 .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/08/10 08:05 upstream 9420f1ce0186 70301872 .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/09 22:52 upstream 06a81c1c7db9 70301872 .config console log report syz ci-upstream-kasan-gce-root
2020/08/09 22:48 upstream 06a81c1c7db9 70301872 .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/09 11:24 upstream 06a81c1c7db9 f721e4a0 .config console log report syz ci-upstream-kasan-gce-smack-root
2020/08/08 05:02 upstream 5631c5e0eb90 ff51e522 .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/08/13 05:28 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-smack-root
2020/08/12 21:47 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-smack-root
2020/08/12 21:10 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-selinux-root
2020/08/12 21:08 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-smack-root
2020/08/12 21:08 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-smack-root
2020/08/12 21:03 upstream fb893de323e2 bc15f7db .config console log report ci-upstream-kasan-gce-root
2020/08/09 22:29 upstream 06a81c1c7db9 70301872 .config console log report ci-upstream-kasan-gce-root
2020/08/09 22:27 upstream 06a81c1c7db9 70301872 .config console log report ci-upstream-kasan-gce-smack-root
2020/08/08 03:13 upstream 5631c5e0eb90 ff51e522 .config console log report ci-upstream-kasan-gce-selinux-root
2020/08/13 06:29 linux-next bc09acc9f224 bc15f7db .config console log report ci-upstream-linux-next-kasan-gce-root
2020/08/13 05:27 linux-next bc09acc9f224 bc15f7db .config console log report ci-upstream-linux-next-kasan-gce-root
2020/08/12 21:47 linux-next bc09acc9f224 bc15f7db .config console log report ci-upstream-linux-next-kasan-gce-root
2020/08/12 21:10 linux-next bc09acc9f224 bc15f7db .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.