[PATCH 05/22] [PATCH] smbfs: Fix slab corruption in samba error path

Chris Wright
2006-05-17T22:30:33Z

[-- Attachment #1: smbfs-fix-slab-corruption-in-samba-error-path.patch --]
[-- Type: text/plain, Size: 8252 bytes --]

-stable review patch. If anyone has any objections, please let us know.
------------------

Yesterday, I got the following error with 2.6.16.13 during a file copy from
a smb filesystem over a wireless link. I guess there was some error on the
wireless link, which in turn caused an error condition for the smb
filesystem.

In the log, smb_file_read reports error=4294966784 (0xfffffe00), which also
shows up in the slab dumps, and also is -ERESTARTSYS. Error code 27499
corresponds to 0x6b6b, so the rq_errno field seems to be the only one being
set after freeing the slab.

In smb_add_request (which is the only place in smbfs where I found
ERESTARTSYS), I found the following:

if (!timeleft || signal_pending(current)) {
/*
* On timeout or on interrupt we want to try and remove the
* request from the recvq/xmitq.
*/
smb_lock_server(server);
if (!(req->rq_flags & SMB_REQ_RECEIVED)) {
list_del_init(&req->rq_queue);
smb_rput(req);
}
smb_unlock_server(server);
}
[...]
if (signal_pending(current))
req->rq_errno = -ERESTARTSYS;

I guess that some codepath like smbiod_flush() caused the request to be
removed from the queue, and smb_rput(req) be called, without
SMB_REQ_RECEIVED being set. This violates an asumption made by the quoted
code.

Then, the above code calls smb_rput(req) again, the req gets freed, and
req->rq_errno = -ERESTARTSYS writes into the already freed slab. As
list_del_init doesn't cause an error if called multiple times, that does
cause the observed behaviour (freed slab with rq_errno=-ERESTARTSYS).

If this observation is correct, the following patch should fix it.

I wonder why the smb code uses list_del_init everywhere - using list_del
instead would catch such situations by poisoning the next and prev
pointers.

May 4 23:29:21 knautsch kernel: [17180085.456000] ipw2200: Firmware error detected. Restarting.
May 4 23:29:21 knautsch kernel: [17180085.456000] ipw2200: Sysfs 'error' log captured.
May 4 23:33:02 knautsch kernel: [17180306.316000] ipw2200: Firmware error detected. Restarting.
May 4 23:33:02 knautsch kernel: [17180306.316000] ipw2200: Sysfs 'error' log already exists.
May 4 23:33:02 knautsch kernel: [17180306.968000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:34:18 knautsch kernel: [17180383.256000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:34:18 knautsch kernel: [17180383.284000] SMB connection re-established (-5)
May 4 23:37:19 knautsch kernel: [17180563.956000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:40:09 knautsch kernel: [17180733.636000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:40:26 knautsch kernel: [17180750.700000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:43:02 knautsch kernel: [17180907.304000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:43:08 knautsch kernel: [17180912.324000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:43:34 knautsch kernel: [17180938.416000] smb_errno: class Unknown, code 27499 from command 0x6b
May 4 23:43:34 knautsch kernel: [17180938.416000] Slab corruption: start=c4ebe09c, len=244
May 4 23:43:34 knautsch kernel: [17180938.416000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:43:34 knautsch kernel: [17180938.416000] Last user: [<e087b903>](smb_rput+0x53/0x90 [smbfs])
May 4 23:43:34 knautsch kernel: [17180938.416000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6a 6b 6b 6b 6b 6b 6b 6b
May 4 23:43:34 knautsch kernel: [17180938.416000] 0f0: 00 fe ff ff
May 4 23:43:34 knautsch kernel: [17180938.416000] Next obj: start=c4ebe19c, len=244
May 4 23:43:34 knautsch kernel: [17180938.416000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:43:34 knautsch kernel: [17180938.416000] Last user: [<00000000>](_stext+0x3feffde0/0x30)
May 4 23:43:34 knautsch kernel: [17180938.416000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:43:34 knautsch kernel: [17180938.416000] 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:43:34 knautsch kernel: [17180938.460000] SMB connection re-established (-5)
May 4 23:43:42 knautsch kernel: [17180946.292000] ipw2200: Firmware error detected. Restarting.
May 4 23:43:42 knautsch kernel: [17180946.292000] ipw2200: Sysfs 'error' log already exists.
May 4 23:45:04 knautsch kernel: [17181028.752000] ipw2200: Firmware error detected. Restarting.
May 4 23:45:04 knautsch kernel: [17181028.752000] ipw2200: Sysfs 'error' log already exists.
May 4 23:45:05 knautsch kernel: [17181029.868000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:45:36 knautsch kernel: [17181060.984000] smb_errno: class Unknown, code 27499 from command 0x6b
May 4 23:45:36 knautsch kernel: [17181060.984000] Slab corruption: start=c4ebe09c, len=244
May 4 23:45:36 knautsch kernel: [17181060.984000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:45:36 knautsch kernel: [17181060.984000] Last user: [<e087b903>](smb_rput+0x53/0x90 [smbfs])
May 4 23:45:36 knautsch kernel: [17181060.984000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6a 6b 6b 6b 6b 6b 6b 6b
May 4 23:45:36 knautsch kernel: [17181060.984000] 0f0: 00 fe ff ff
May 4 23:45:36 knautsch kernel: [17181060.984000] Next obj: start=c4ebe19c, len=244
May 4 23:45:36 knautsch kernel: [17181060.984000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:45:36 knautsch kernel: [17181060.984000] Last user: [<00000000>](_stext+0x3feffde0/0x30)
May 4 23:45:36 knautsch kernel: [17181060.984000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:45:36 knautsch kernel: [17181060.984000] 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:45:36 knautsch kernel: [17181061.024000] SMB connection re-established (-5)
May 4 23:46:17 knautsch kernel: [17181102.132000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:47:46 knautsch kernel: [17181190.468000] smb_errno: class Unknown, code 27499 from command 0x6b
May 4 23:47:46 knautsch kernel: [17181190.468000] Slab corruption: start=c4ebe09c, len=244
May 4 23:47:46 knautsch kernel: [17181190.468000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:47:46 knautsch kernel: [17181190.468000] Last user: [<e087b903>](smb_rput+0x53/0x90 [smbfs])
May 4 23:47:46 knautsch kernel: [17181190.468000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6a 6b 6b 6b 6b 6b 6b 6b
May 4 23:47:46 knautsch kernel: [17181190.468000] 0f0: 00 fe ff ff
May 4 23:47:46 knautsch kernel: [17181190.468000] Next obj: start=c4ebe19c, len=244
May 4 23:47:46 knautsch kernel: [17181190.468000] Redzone: 0x5a2cf071/0x5a2cf071.
May 4 23:47:46 knautsch kernel: [17181190.468000] Last user: [<00000000>](_stext+0x3feffde0/0x30)
May 4 23:47:46 knautsch kernel: [17181190.468000] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:47:46 knautsch kernel: [17181190.468000] 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
May 4 23:47:46 knautsch kernel: [17181190.492000] SMB connection re-established (-5)
May 4 23:49:20 knautsch kernel: [17181284.828000] smb_file_read: //some_file validation failed, error=4294966784
May 4 23:49:39 knautsch kernel: [17181303.896000] smb_file_read: //some_file validation failed, error=4294966784

Signed-off-by: Jan Niehusmann <jan@gondor.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

fs/smbfs/request.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- linux-2.6.16.16.orig/fs/smbfs/request.c
+++ linux-2.6.16.16/fs/smbfs/request.c
@@ -339,9 +339,11 @@ int smb_add_request(struct smb_request *
/*
* On timeout or on interrupt we want to try and remove the
* request from the recvq/xmitq.
+ * First check if the request is still part of a queue. (May
+ * have been removed by some error condition)
*/
smb_lock_server(server);
- if (!(req->rq_flags & SMB_REQ_RECEIVED)) {
+ if (!list_empty(&req->rq_queue)) {
list_del_init(&req->rq_queue);
smb_rput(req);
}

--