[PATCH 4.19 143/149] cifs: allow calling SMB2_xxx_free(NULL)

[Greg Kroah-Hartman]

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

------------------

From: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>

commit 32a1fb36f6e50183871c2c1fcf5493c633e84732 upstream.

Change these free functions to allow passing NULL as the argument and
treat it as a no-op just like free(NULL) would.
Or, if rqst->rq_iov is NULL.

The second scenario could happen for smb2_queryfs() if the call
to SMB2_query_info_init() fails and we go to qfs_exit to clean up
and free all resources.
In that case we have not yet assigned rqst[2].rq_iov and thus
the rq_iov dereference in SMB2_close_free() will cause a NULL pointer
dereference.

[ bp: upstream patch also fixes SMB2_set_info_free which was introduced in 4.20 ]

Fixes:  1eb9fb52040f ("cifs: create SMB2_open_init()/SMB2_open_free() helpers")

Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Reviewed-by: Aurelien Aptel <aaptel@xxxxxxxx>
CC: Stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/cifs/smb2pdu.c |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2243,10 +2243,12 @@ SMB2_open_free(struct smb_rqst *rqst)
 {
 	int i;
 
-	cifs_small_buf_release(rqst->rq_iov[0].iov_base);
-	for (i = 1; i < rqst->rq_nvec; i++)
-		if (rqst->rq_iov[i].iov_base != smb2_padding)
-			kfree(rqst->rq_iov[i].iov_base);
+	if (rqst && rqst->rq_iov) {
+		cifs_small_buf_release(rqst->rq_iov[0].iov_base);
+		for (i = 1; i < rqst->rq_nvec; i++)
+			if (rqst->rq_iov[i].iov_base != smb2_padding)
+				kfree(rqst->rq_iov[i].iov_base);
+	}
 }
 
 int
@@ -2535,7 +2537,8 @@ SMB2_close_init(struct cifs_tcon *tcon,
 void
 SMB2_close_free(struct smb_rqst *rqst)
 {
-	cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
+	if (rqst && rqst->rq_iov)
+		cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
 }
 
 int
@@ -2685,7 +2688,8 @@ SMB2_query_info_init(struct cifs_tcon *t
 void
 SMB2_query_info_free(struct smb_rqst *rqst)
 {
-	cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
+	if (rqst && rqst->rq_iov)
+		cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
 }
 
 static int