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authorJeff Layton <jlayton@redhat.com>2011-04-02 07:34:30 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-21 14:32:21 -0700
commit3b76dafa88d04ea91e9b16a4cd7489977d60602b (patch)
tree2268306c6fa4b2b14194ebdfeeadf7eeef43b3d4 /fs
parent591c80b5a9a9331a9b2a6d1b7d9b97d3445107c9 (diff)
downloadlwn-3b76dafa88d04ea91e9b16a4cd7489977d60602b.tar.gz
lwn-3b76dafa88d04ea91e9b16a4cd7489977d60602b.zip
cifs: wrap received signature check in srv_mutex
commit 157c249114508aa71daa308a426e15d81a4eed00 upstream. While testing my patchset to fix asynchronous writes, I hit a bunch of signature problems when testing with signing on. The problem seems to be that signature checks on receive can be running at the same time as a process that is sending, or even that multiple receives can be checking signatures at the same time, clobbering the same data structures. While we're at it, clean up the comments over cifs_calculate_signature and add a note that the srv_mutex should be held when calling this function. This patch seems to fix the problems for me, but I'm not clear on whether it's the best approach. If it is, then this should probably go to stable too. Cc: Shirish Pargaonkar <shirishpargaonkar@gmail.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs')
-rw-r--r--fs/cifs/cifsencrypt.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index a51585f9852b..96b9a34db48b 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -30,12 +30,13 @@
#include <linux/ctype.h>
#include <linux/random.h>
-/* Calculate and return the CIFS signature based on the mac key and SMB PDU */
-/* the 16 byte signature must be allocated by the caller */
-/* Note we only use the 1st eight bytes */
-/* Note that the smb header signature field on input contains the
- sequence number before this function is called */
-
+/*
+ * Calculate and return the CIFS signature based on the mac key and SMB PDU.
+ * The 16 byte signature must be allocated by the caller. Note we only use the
+ * 1st eight bytes and that the smb header signature field on input contains
+ * the sequence number before this function is called. Also, this function
+ * should be called with the server->srv_mutex held.
+ */
static int cifs_calculate_signature(const struct smb_hdr *cifs_pdu,
struct TCP_Server_Info *server, char *signature)
{
@@ -209,8 +210,10 @@ int cifs_verify_signature(struct smb_hdr *cifs_pdu,
cpu_to_le32(expected_sequence_number);
cifs_pdu->Signature.Sequence.Reserved = 0;
+ mutex_lock(&server->srv_mutex);
rc = cifs_calculate_signature(cifs_pdu, server,
what_we_think_sig_should_be);
+ mutex_unlock(&server->srv_mutex);
if (rc)
return rc;