configfs: fix slab-UAF Write in config_item_put
PATCH v3 1/1 configfs: fix slab-UAF Write in config_item_put
syzbot reported:
BUG: KASAN: slab-use-after-free in config_item_put+0x26/0x90
fs/configfs/item.c:149
Call Trace:
...
config_item_put+0x26/0x90 fs/configfs/item.c:149
configfs_symlink+0x6be/0x11d0 fs/configfs/symlink.c:225
vfs_symlink+0x18b/0x330 fs/namei.c:5823
filename_symlinkat+0x1cd/0x420 fs/namei.c:5848
Allocated by task 5712:
...
nvmet_ports_make+0xe6/0xf00 drivers/nvme/target/configfs.c:2054
configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369
vfs_mkdir+0x408/0x620 fs/namei.c:5439
filename_mkdirat+0x289/0x520 fs/namei.c:5472
Freed by task 5712:
...
config_item_cleanup fs/configfs/item.c:128 [inline]
config_item_release+0x13a/0x2d0 fs/configfs/item.c:137
configfs_rmdir+0x885/0x950 fs/configfs/dir.c:1580
vfs_rmdir+0x3e9/0x6b0 fs/namei.c:5544
filename_rmdir+0x292/0x520 fs/namei.c:5601configfs_symlink() takes a reference on parent_item, drops the directory inode lock around get_target(), and puts the reference at the end. If a concurrent rmdir removes the group in that window, and parent_item is a default group embedded in a larger object (e.g. nvmet_port.subsys_group), the reference does not keep the containing object alive. The object is freed, and the final config_item_put(parent_item) hits freed memory.
The syzbot reproducer hits this by racing symlinkat() into ports/1/subsystems against rmdir of ports/1.
Fix this by not holding parent_item across the unlocked window: put it before inode_unlock(), and look it up again from dentry->d_parent after inode_lock(), returning -ENOENT if the lookup fails.
That is not enough on its own. configfs_get_config_item() only fails if the parent dentry was unhashed, but if simple_rmdir() fails, rmdir skips d_drop() and the dentry stays hashed even though the directory is already detached. Default groups are detached through configfs_detach_group(), which marks children S_DEAD, so also check IS_DEADDIR(dir) after retaking the lock and return -ENOENT.
Reported-by [email protected]
Tested-by [email protected]
Signed-off-by Drif Abdelmalek Mohamed Said <[email protected]>
---
v3:
- Removed redundant null assignment to parent_item
- Simplified commit body to not rely heavily on repro
explain bug and fix logic
v2: https://lore.kernel.org/all/[email protected]/T/
v1: https://lore.kernel.org/all/[email protected]/T/
fs/configfs/symlink.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
fs/configfs/symlink.c +15 -0
@@ -196,12 +196,26 @@ int configfs_symlink(const struct mnt_idmap *idmap, struct inode *dir,* * AV, a thoroughly annoyed bastard. */ + +/* Put the reference back, retake and check after relocking */ +config_item_put (parent_item);inode_unlock (dir); ret =get_target (symname, &target_item, &target_sd, dentry->d_sb);inode_lock (dir);if (ret) goto out_put; +if (IS_DEADDIR (dir)) { + ret = -ENOENT ; + goto out_put_target; + } + + parent_item =configfs_get_config_item (dentry->d_parent); +if (!parent_item) { + ret = -ENOENT ; + goto out_put_target; + } +if (dentry->d_inode ||d_unhashed (dentry)) ret = -EEXIST ;else
@@ -218,6 +232,7 @@ int configfs_symlink(const struct mnt_idmap *idmap, struct inode *dir, target_item); } +out_put_target:configfs_put (target_sd);config_item_put (target_item);
Signature · 1 line
2.43.0
Breno Leitao
maintainerQuoted 3 lines · Drif Abdelmalek Mohamed Said
---
v3:
- Removed redundant null assignment toparent_item
It wasn't redundant, see below.
fs/configfs/symlink.c int configfs_symlink(const struct mnt_idmap *idmap, struct inode *dir, · line 211
Quoted 5 lines
fs/configfs/symlink.c +4
-0+if (IS_DEADDIR (dir)) { + ret = -ENOENT ; + goto out_put_target; + }
I am seeing the following when running this version:
refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:34 at refcount_warn_saturate+0x76/0xd0, CPU#1: ln/172 Call Trace:
Can you help me to understand how this was tested?
Thanks,
--breno
Hello Breno,
Quoted 2 lines
refcount_t: addition on 0; use-after-free.WARNING: lib/refcount.c:34 at refcount_warn_saturate+0x76/0xd0, CPU#1: ln/172
So i think this is caused because i removed the null assignment on parent_item, so it catches
what parent_item pointed to when refcount was 0 but before the free, and this is actually my mistake, i sent a syztest with the old parent_item = NULL after the put,
and that is actually important here, because it protects uaf in out_put and out_put_target,
so we either move the if (IS_DEADDIR(dir)) check after configfs_get_config_item and omitparent_item = NULL on the 1st lock, or we keep it as is. Should i send v4 or you can apply this directly (if good enough)
Cordially,
Breno Leitao
maintainerQuoted 1 line · DRIF ABDELMALEK MOHAMED SAID
Should i send v4 or you can apply this directly (if good enough)
no worries, I can handle it here.
Thanks for your fix,
--breno
syzbot ci has tested the following series
syzbot ci has tested the following series
[v3] configfs: fix slab-UAF Write in config_item_put
https://lore.kernel.org/all/[email protected]
* [PATCH v3] configfs: fix slab-UAF Write in config_item_put
and found the following issues:
* KASAN: slab-use-after-free Write in config_item_get
* kernel BUG in config_item_get
* kernel BUG in configfs_symlink
Full report is available here:
https://ci.syzbot.org/series/6e7e3ace-c083-43ff-9d6c-4b65ef15bd2f
***
KASAN: slab-use-after-free Write in config_item_get
tree: vfs URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git base: 691edd89507f8977eb8831892c3b460edc79d73c arch: amd64 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/b34863a5-8646-4b81-a3b6-8d7c722db7f8/config syz repro: https://ci.syzbot.org/findings/4586cba9-fdc4-48a1-bbe4-43b477a6d2cf/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline] BUG: KASAN: slab-use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] BUG: KASAN: slab-use-after-free in __refcount_add include/linux/refcount.h:283 [inline] BUG: KASAN: slab-use-after-free in __refcount_inc include/linux/refcount.h:366 [inline] BUG: KASAN: slab-use-after-free in refcount_inc include/linux/refcount.h:383 [inline] BUG: KASAN: slab-use-after-free in kref_get include/linux/kref.h:45 [inline] BUG: KASAN: slab-use-after-free in config_item_get+0x26/0x90 fs/configfs/item.c:104 Write of size 4 at addr ffff8881191a501c by task syz.1.22/5911 CPU: 0 UID: 0 PID: 5911 Comm: syz.1.22 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description+0x55/0x1e0 mm/kasan/report.c:378 print_report+0x58/0x70 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200 instrument_atomic_read_write include/linux/instrumented.h:112 [inline] atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] __refcount_add include/linux/refcount.h:283 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] kref_get include/linux/kref.h:45 [inline] config_item_get+0x26/0x90 fs/configfs/item.c:104 configfs_get_config_item fs/configfs/configfs_internal.h:127 [inline] configfs_symlink+0x17d/0xa60 fs/configfs/symlink.c:167 vfs_symlink+0x18e/0x370 fs/namei.c:5812 filename_symlinkat+0x1a5/0x430 fs/namei.c:5837 __do_sys_symlinkat fs/namei.c:5857 [inline] __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5852 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ffbd0f9fb19 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffbd1dfb028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a RAX: ffffffffffffffda RBX: 00007ffbd1225fa0 RCX: 00007ffbd0f9fb19 RDX: 0000200000000780 RSI: ffffffffffffff9c RDI: 0000200000000740 RBP: 00007ffbd1037b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffbd1226038 R14: 00007ffbd1225fa0 R15: 00007ffeea8f6108 </TASK> Allocated by task 5903: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:409 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x31c/0x600 mm/slub.c:5680 _kmalloc_noprof include/linux/slab.h:991 [inline] _kzalloc_noprof include/linux/slab.h:1312 [inline] config_desc_make+0x23e/0x620 drivers/usb/gadget/configfs.c:730 configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369 vfs_mkdir+0x411/0x660 fs/namei.c:5428 filename_mkdirat+0x284/0x550 fs/namei.c:5461 __do_sys_mkdirat fs/namei.c:5482 [inline] __se_sys_mkdirat+0x35/0x150 fs/namei.c:5479 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5908: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:264 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2780 [inline] slab_free mm/slub.c:6630 [inline] kfree+0x1c5/0x650 mm/slub.c:6923 config_item_cleanup fs/configfs/item.c:128 [inline] config_item_release+0x13a/0x2d0 fs/configfs/item.c:137 configfs_symlink+0x7b4/0xa60 fs/configfs/symlink.c:240 vfs_symlink+0x18e/0x370 fs/namei.c:5812 filename_symlinkat+0x1a5/0x430 fs/namei.c:5837 __do_sys_symlinkat fs/namei.c:5857 [inline] __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5852 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff8881191a5000 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 28 bytes inside of
freed 1024-byte region [ffff8881191a5000, ffff8881191a5400)
The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1191a0 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff) page_type: f5(slab) raw: 017ff00000000040 ffff888100041dc0 dead000000000100 dead000000000122 raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff888100041dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 017ff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5697, tgid 5697 (kworker/u8:3), ts 73161807282
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1856
prep_new_page mm/page_alloc.c:1864 [inline]
get_page_from_freelist+0x220f/0x2280 mm/page_alloc.c:3935
__alloc_frozen_pages_noprof+0x1fe/0x410 mm/page_alloc.c:5444
alloc_slab_page mm/slub.c:3384 [inline]
allocate_slab+0x7d/0x5e0 mm/slub.c:3499
new_slab mm/slub.c:3550 [inline]
refill_objects+0x2d5/0x350 mm/slub.c:7539
refill_sheaf mm/slub.c:2917 [inline]
__pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4811
alloc_from_pcs mm/slub.c:4887 [inline]
slab_alloc_node mm/slub.c:5021 [inline]
__do_kmalloc_node mm/slub.c:5530 [inline]
__kmalloc_noprof+0x476/0x710 mm/slub.c:5556
_kmalloc_noprof include/linux/slab.h:995 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
neigh_alloc net/core/neighbour.c:525 [inline]
___neigh_create+0x6da/0x21f0 net/core/neighbour.c:659
ip6_finish_output2+0xe06/0x1460 net/ipv6/ip6_output.c:130
NF_HOOK_COND include/linux/netfilter.h:314 [inline]
ip6_output+0x337/0x540 net/ipv6/ip6_output.c:248
dst_output include/net/dst.h:472 [inline]
NF_HOOK include/linux/netfilter.h:325 [inline]
ndisc_send_skb+0xcb2/0x1650 net/ipv6/ndisc.c:513
ndisc_send_ns+0xd7/0x160 net/ipv6/ndisc.c:672
addrconf_dad_work+0xa8d/0x15c0 net/ipv6/addrconf.c:4343
process_one_work kernel/workqueue.c:3495 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
kthread+0x38b/0x480 kernel/kthread.c:436
page last free pid 5696 tgid 5696 ts 63917357465 stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
__free_pages_prepare mm/page_alloc.c:1403 [inline]
__free_frozen_pages+0xc97/0xd90 mm/page_alloc.c:2954
__slab_free+0x269/0x2c0 mm/slub.c:5926
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:361
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4720 [inline]
slab_alloc_node mm/slub.c:5033 [inline]
kmem_cache_alloc_noprof+0x2b4/0x600 mm/slub.c:5047
__proc_create+0x55d/0xad0 fs/proc/generic.c:462
proc_create_reg fs/proc/generic.c:606 [inline]
proc_create_data+0xa5/0x190 fs/proc/generic.c:620
nfs_net_init+0x1a7/0x290 fs/nfs/inode.c:2777
ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
setup_net+0x118/0x350 net/core/net_namespace.c:443
copy_net_ns+0x536/0x770 net/core/net_namespace.c:584
create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
unshare_nsproxy_namespaces+0x144/0x190 kernel/nsproxy.c:234
ksys_unshare+0x532/0x890 kernel/fork.c:3320
__do_sys_unshare kernel/fork.c:3386 [inline]
__se_sys_unshare kernel/fork.c:3384 [inline]
__x64_sys_unshare+0x38/0x50 kernel/fork.c:3384
Memory state around the buggy address:
ffff8881191a4f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881191a4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881191a5000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881191a5080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881191a5100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================***
kernel BUG in config_item_get
tree: vfs URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git base: 691edd89507f8977eb8831892c3b460edc79d73c arch: amd64 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/b34863a5-8646-4b81-a3b6-8d7c722db7f8/config syz repro: https://ci.syzbot.org/findings/1475de5c-5602-4f7c-97d8-fa318d3969f7/syz_repro
refcount_t: addition on 0; use-after-free.
------------[ cut here ]------------ kernel BUG at lib/refcount.c:34! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 5904 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0xf0/0x110 lib/refcount.c:34 Code: 80 c1 03 38 c1 0f 8c 6a ff ff ff 4c 89 f7 e8 a7 10 51 fd e9 5d ff ff ff e8 fd c2 d9 fc 48 c7 c7 a0 98 8c 8c e8 e1 73 38 fc 90 <0f> 0b e8 e9 c2 d9 fc 48 c7 c7 20 99 8c 8c e8 cd 73 38 fc 90 0f 0b RSP: 0018:ffffc900030bfc68 EFLAGS: 00010246 RAX: 000000000000002a RBX: 0000000000000002 RCX: ca30be1f7752be00 RDX: 0000000000000000 RSI: 8000000000000001 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffc900030bf9e7 R09: 1ffff92000617f3c R10: dffffc0000000000 R11: fffff52000617f3d R12: 1ffff1102365c80a R13: ffff88811776d218 R14: ffff888117f184b4 R15: ffff8881ba75a598 FS: 00007fcbbc6696c0(0000) GS:ffff88818be0d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fcbbb6716a0 CR3: 0000000117a68000 CR4: 00000000000006f0 Call Trace: <TASK> __refcount_add include/linux/refcount.h:-1 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] kref_get include/linux/kref.h:45 [inline] config_item_get+0x88/0x90 fs/configfs/item.c:104 configfs_get_config_item fs/configfs/configfs_internal.h:127 [inline] configfs_symlink+0x17d/0xa60 fs/configfs/symlink.c:167 vfs_symlink+0x18e/0x370 fs/namei.c:5812 filename_symlinkat+0x1a5/0x430 fs/namei.c:5837 __do_sys_symlinkat fs/namei.c:5857 [inline] __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5852 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcbbb79fb19 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fcbbc669028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a RAX: ffffffffffffffda RBX: 00007fcbbba25fa0 RCX: 00007fcbbb79fb19 RDX: 0000200000000840 RSI: ffffffffffffff9c RDI: 0000200000000800 RBP: 00007fcbbb837b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fcbbba26038 R14: 00007fcbbba25fa0 R15: 00007ffd984fbca8 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:refcount_warn_saturate+0xf0/0x110 lib/refcount.c:34 Code: 80 c1 03 38 c1 0f 8c 6a ff ff ff 4c 89 f7 e8 a7 10 51 fd e9 5d ff ff ff e8 fd c2 d9 fc 48 c7 c7 a0 98 8c 8c e8 e1 73 38 fc 90 <0f> 0b e8 e9 c2 d9 fc 48 c7 c7 20 99 8c 8c e8 cd 73 38 fc 90 0f 0b RSP: 0018:ffffc900030bfc68 EFLAGS: 00010246 RAX: 000000000000002a RBX: 0000000000000002 RCX: ca30be1f7752be00 RDX: 0000000000000000 RSI: 8000000000000001 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffc900030bf9e7 R09: 1ffff92000617f3c R10: dffffc0000000000 R11: fffff52000617f3d R12: 1ffff1102365c80a R13: ffff88811776d218 R14: ffff888117f184b4 R15: ffff8881ba75a598 FS: 00007fcbbc6696c0(0000) GS:ffff88818be0d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fcbbb6716a0 CR3: 0000000117a68000 CR4: 00000000000006f0
***
kernel BUG in configfs_symlink
tree: vfs URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git base: 691edd89507f8977eb8831892c3b460edc79d73c arch: amd64 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/b34863a5-8646-4b81-a3b6-8d7c722db7f8/config
refcount_t: underflow; use-after-free.
------------[ cut here ]------------ kernel BUG at lib/refcount.c:37! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 5815 Comm: syz.2.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x104/0x110 Code: 5d ff ff ff e8 fd c2 d9 fc 48 c7 c7 a0 98 8c 8c e8 e1 73 38 fc 90 0f 0b e8 e9 c2 d9 fc 48 c7 c7 20 99 8c 8c e8 cd 73 38 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffc90006787c88 EFLAGS: 00010246 RAX: 0000000000000026 RBX: 0000000000000003 RCX: 7d2d66e1f00cde00 RDX: 0000000000000000 RSI: 8000000000000000 RDI: 0000000000000000 RBP: ffffc90006787d88 R08: ffffc90006787a07 R09: 1ffff92000cf0f40 R10: dffffc0000000000 R11: fffff52000cf0f41 R12: 1ffff110228fe2e2 R13: 00000000fffffffe R14: ffff88816f8584b4 R15: 1ffff92000cf0fa0 FS: 00007f3b9041d6c0(0000) GS:ffff8882a780d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007feda95bb440 CR3: 0000000110044000 CR4: 00000000000006f0 Call Trace: <TASK> configfs_symlink+0x7b4/0xa60 vfs_symlink+0x18e/0x370 filename_symlinkat+0x1a5/0x430 __se_sys_symlinkat+0x4e/0x2b0 do_syscall_64+0x166/0x520 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3b8f59fb19 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3b9041d028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a RAX: ffffffffffffffda RBX: 00007f3b8f826090 RCX: 00007f3b8f59fb19 RDX: 0000200000000840 RSI: ffffffffffffff9c RDI: 0000200000000800 RBP: 00007f3b8f637b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3b8f826128 R14: 00007f3b8f826090 R15: 00007ffcd3b51e38 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:refcount_warn_saturate+0x104/0x110 Code: 5d ff ff ff e8 fd c2 d9 fc 48 c7 c7 a0 98 8c 8c e8 e1 73 38 fc 90 0f 0b e8 e9 c2 d9 fc 48 c7 c7 20 99 8c 8c e8 cd 73 38 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffc90006787c88 EFLAGS: 00010246 RAX: 0000000000000026 RBX: 0000000000000003 RCX: 7d2d66e1f00cde00 RDX: 0000000000000000 RSI: 8000000000000000 RDI: 0000000000000000 RBP: ffffc90006787d88 R08: ffffc90006787a07 R09: 1ffff92000cf0f40 R10: dffffc0000000000 R11: fffff52000cf0f41 R12: 1ffff110228fe2e2 R13: 00000000fffffffe R14: ffff88816f8584b4 R15: 1ffff92000cf0fa0 FS: 00007f3b9041d6c0(0000) GS:ffff88818be0d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fd9936587f0 CR3: 0000000110044000 CR4: 00000000000006f0
***
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---
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Quoted 2 lines · Drif Abdelmalek Mohamed Said
v3:
- Removed redundant null assignment toparent_item
Applied to for-next, with that assignment restored, so there is no need for a v4.
Thanks,
--breno