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Message-ID: <20250516091256.2756826-2-wangzhaolong1@huawei.com>
Date: Fri, 16 May 2025 17:12:55 +0800
From: Wang Zhaolong <wangzhaolong1@...wei.com>
To: <sfrench@...ba.org>, <sfrench@...ibm.com>
CC: <linux-cifs@...r.kernel.org>, <samba-technical@...ts.samba.org>,
<linux-kernel@...r.kernel.org>, <chengzhihao1@...wei.com>,
<wangzhaolong1@...wei.com>, <yi.zhang@...wei.com>, <yangerkun@...wei.com>
Subject: [PATCH V2 1/2] smb: client: Fix use-after-free in cifs_fill_dirent
There is a race condition in the readdir concurrency process, which may
access the rsp buffer after it has been released, triggering the
following KASAN warning.
==================================================================
BUG: KASAN: slab-use-after-free in cifs_fill_dirent+0xb03/0xb60 [cifs]
Read of size 4 at addr ffff8880099b819c by task a.out/342975
CPU: 2 UID: 0 PID: 342975 Comm: a.out Not tainted 6.15.0-rc6+ #240 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x53/0x70
print_report+0xce/0x640
kasan_report+0xb8/0xf0
cifs_fill_dirent+0xb03/0xb60 [cifs]
cifs_readdir+0x12cb/0x3190 [cifs]
iterate_dir+0x1a1/0x520
__x64_sys_getdents+0x134/0x220
do_syscall_64+0x4b/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f996f64b9f9
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 0d f7 c3 0c 00 f7 d8 64 89 8
RSP: 002b:00007f996f53de78 EFLAGS: 00000207 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f996f53ecdc RCX: 00007f996f64b9f9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f996f53dea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000207 R12: ffffffffffffff88
R13: 0000000000000000 R14: 00007ffc8cd9a500 R15: 00007f996f51e000
</TASK>
Allocated by task 408:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
__kasan_slab_alloc+0x6e/0x70
kmem_cache_alloc_noprof+0x117/0x3d0
mempool_alloc_noprof+0xf2/0x2c0
cifs_buf_get+0x36/0x80 [cifs]
allocate_buffers+0x1d2/0x330 [cifs]
cifs_demultiplex_thread+0x22b/0x2690 [cifs]
kthread+0x394/0x720
ret_from_fork+0x34/0x70
ret_from_fork_asm+0x1a/0x30
Freed by task 342979:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x37/0x50
kmem_cache_free+0x2b8/0x500
cifs_buf_release+0x3c/0x70 [cifs]
cifs_readdir+0x1c97/0x3190 [cifs]
iterate_dir+0x1a1/0x520
__x64_sys_getdents64+0x134/0x220
do_syscall_64+0x4b/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The buggy address belongs to the object at ffff8880099b8000
which belongs to the cache cifs_request of size 16588
The buggy address is located 412 bytes inside of
freed 16588-byte region [ffff8880099b8000, ffff8880099bc0cc)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x99b8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000
head: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001
head: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000
head: 0080000000000003 ffffea0000266e01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880099b8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880099b8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880099b8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880099b8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880099b8280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
POC is available in the link [1].
The problem triggering process is as follows:
Process 1 Process 2
-----------------------------------------------------------------
cifs_readdir
/* file->private_data == NULL */
initiate_cifs_search
cifsFile = kzalloc(sizeof(struct cifsFileInfo), GFP_KERNEL);
smb2_query_dir_first ->query_dir_first()
SMB2_query_directory
SMB2_query_directory_init
cifs_send_recv
smb2_parse_query_directory
srch_inf->ntwrk_buf_start = (char *)rsp;
srch_inf->srch_entries_start = (char *)rsp + ...
srch_inf->last_entry = (char *)rsp + ...
srch_inf->smallBuf = true;
find_cifs_entry
/* if (cfile->srch_inf.ntwrk_buf_start) */
cifs_small_buf_release(cfile->srch_inf // free
cifs_readdir ->iterate_shared()
/* file->private_data != NULL */
find_cifs_entry
/* in while (...) loop */
smb2_query_dir_next ->query_dir_next()
SMB2_query_directory
SMB2_query_directory_init
cifs_send_recv
compound_send_recv
smb_send_rqst
__smb_send_rqst
rc = -ERESTARTSYS;
/* if (fatal_signal_pending()) */
goto out;
return rc
/* if (cfile->srch_inf.last_entry) */
cifs_save_resume_key()
cifs_fill_dirent // UAF
/* if (rc) */
return -ENOENT;
Fix this by ensuring the return code is checked before using pointers
from the srch_inf.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220131 [1]
Fixes: a364bc0b37f1 ("[CIFS] fix saving of resume key before CIFSFindNext")
Cc: stable@...r.kernel.org
Signed-off-by: Wang Zhaolong <wangzhaolong1@...wei.com>
---
fs/smb/client/readdir.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index 50f96259d9ad..67d7dd64b5e2 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -754,15 +754,15 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
(rc == 0) && !cfile->srch_inf.endOfSearch) {
cifs_dbg(FYI, "calling findnext2\n");
rc = server->ops->query_dir_next(xid, tcon, &cfile->fid,
search_flags,
&cfile->srch_inf);
+ if (rc)
+ return -ENOENT;
/* FindFirst/Next set last_entry to NULL on malformed reply */
if (cfile->srch_inf.last_entry)
cifs_save_resume_key(cfile->srch_inf.last_entry, cfile);
- if (rc)
- return -ENOENT;
}
if (index_to_find < cfile->srch_inf.index_of_last_entry) {
/* we found the buffer that contains the entry */
/* scan and find it */
int i;
--
2.39.2
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