[PATCH v2] ksmbd: fix global-out-of-bounds in smb2_find_context_vals

[Namjae Jeon <linkinjeon@xxxxxxxxxx>]

From: Pumpkin <cc85nod@xxxxxxxxx>

Add tag_len argument in smb2_find_context_vals() to avoid out-of-bound
read when create_context's name_len is larger than tag length.

Signed-off-by: Pumpkin <cc85nod@xxxxxxxxx>
---
 v2:
  - add the check if tag len and name len are same before comparing tag
    and name.

 fs/ksmbd/oplock.c  |  5 +++--
 fs/ksmbd/oplock.h  |  2 +-
 fs/ksmbd/smb2pdu.c | 14 +++++++-------
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/ksmbd/oplock.c b/fs/ksmbd/oplock.c
index 2e54ded4d..6d1ccb999 100644
--- a/fs/ksmbd/oplock.c
+++ b/fs/ksmbd/oplock.c
@@ -1449,11 +1449,12 @@ struct lease_ctx_info *parse_lease_state(void *open_req)
  * smb2_find_context_vals() - find a particular context info in open request
  * @open_req:	buffer containing smb2 file open(create) request
  * @tag:	context name to search for
+ * @tag_len:	the length of tag
  *
  * Return:	pointer to requested context, NULL if @str context not found
  *		or error pointer if name length is invalid.
  */
-struct create_context *smb2_find_context_vals(void *open_req, const char *tag)
+struct create_context *smb2_find_context_vals(void *open_req, const char *tag, int tag_len)
 {
 	struct create_context *cc;
 	unsigned int next = 0;
@@ -1492,7 +1493,7 @@ struct create_context *smb2_find_context_vals(void *open_req, const char *tag)
 			return ERR_PTR(-EINVAL);
 
 		name = (char *)cc + name_off;
-		if (memcmp(name, tag, name_len) == 0)
+		if (name_len == tag_len && !memcmp(name, tag, name_len))
 			return cc;
 
 		remain_len -= next;
diff --git a/fs/ksmbd/oplock.h b/fs/ksmbd/oplock.h
index 09753448f..4b0fe6da7 100644
--- a/fs/ksmbd/oplock.h
+++ b/fs/ksmbd/oplock.h
@@ -118,7 +118,7 @@ void create_durable_v2_rsp_buf(char *cc, struct ksmbd_file *fp);
 void create_mxac_rsp_buf(char *cc, int maximal_access);
 void create_disk_id_rsp_buf(char *cc, __u64 file_id, __u64 vol_id);
 void create_posix_rsp_buf(char *cc, struct ksmbd_file *fp);
-struct create_context *smb2_find_context_vals(void *open_req, const char *str);
+struct create_context *smb2_find_context_vals(void *open_req, const char *tag, int tag_len);
 struct oplock_info *lookup_lease_in_table(struct ksmbd_conn *conn,
 					  char *lease_key);
 int find_same_lease_key(struct ksmbd_session *sess, struct ksmbd_inode *ci,
diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index da66abc7c..013eeefd0 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -2492,7 +2492,7 @@ static int smb2_create_sd_buffer(struct ksmbd_work *work,
 		return -ENOENT;
 
 	/* Parse SD BUFFER create contexts */
-	context = smb2_find_context_vals(req, SMB2_CREATE_SD_BUFFER);
+	context = smb2_find_context_vals(req, SMB2_CREATE_SD_BUFFER, 4);
 	if (!context)
 		return -ENOENT;
 	else if (IS_ERR(context))
@@ -2694,7 +2694,7 @@ int smb2_open(struct ksmbd_work *work)
 
 	if (req->CreateContextsOffset) {
 		/* Parse non-durable handle create contexts */
-		context = smb2_find_context_vals(req, SMB2_CREATE_EA_BUFFER);
+		context = smb2_find_context_vals(req, SMB2_CREATE_EA_BUFFER, 4);
 		if (IS_ERR(context)) {
 			rc = PTR_ERR(context);
 			goto err_out1;
@@ -2714,7 +2714,7 @@ int smb2_open(struct ksmbd_work *work)
 		}
 
 		context = smb2_find_context_vals(req,
-						 SMB2_CREATE_QUERY_MAXIMAL_ACCESS_REQUEST);
+						 SMB2_CREATE_QUERY_MAXIMAL_ACCESS_REQUEST, 4);
 		if (IS_ERR(context)) {
 			rc = PTR_ERR(context);
 			goto err_out1;
@@ -2725,7 +2725,7 @@ int smb2_open(struct ksmbd_work *work)
 		}
 
 		context = smb2_find_context_vals(req,
-						 SMB2_CREATE_TIMEWARP_REQUEST);
+						 SMB2_CREATE_TIMEWARP_REQUEST, 4);
 		if (IS_ERR(context)) {
 			rc = PTR_ERR(context);
 			goto err_out1;
@@ -2737,7 +2737,7 @@ int smb2_open(struct ksmbd_work *work)
 
 		if (tcon->posix_extensions) {
 			context = smb2_find_context_vals(req,
-							 SMB2_CREATE_TAG_POSIX);
+							 SMB2_CREATE_TAG_POSIX, 16);
 			if (IS_ERR(context)) {
 				rc = PTR_ERR(context);
 				goto err_out1;
@@ -3136,7 +3136,7 @@ int smb2_open(struct ksmbd_work *work)
 		struct create_alloc_size_req *az_req;
 
 		az_req = (struct create_alloc_size_req *)smb2_find_context_vals(req,
-					SMB2_CREATE_ALLOCATION_SIZE);
+					SMB2_CREATE_ALLOCATION_SIZE, 4);
 		if (IS_ERR(az_req)) {
 			rc = PTR_ERR(az_req);
 			goto err_out;
@@ -3163,7 +3163,7 @@ int smb2_open(struct ksmbd_work *work)
 					    err);
 		}
 
-		context = smb2_find_context_vals(req, SMB2_CREATE_QUERY_ON_DISK_ID);
+		context = smb2_find_context_vals(req, SMB2_CREATE_QUERY_ON_DISK_ID, 4);
 		if (IS_ERR(context)) {
 			rc = PTR_ERR(context);
 			goto err_out;
-- 
2.39.2 (Apple Git-143)