befs: Validate length of long symbolic links.

commit 338d0f0a6fbc82407864606f5b64b75aeb3c70f2 upstream.

Signed-off-by: Timo Warns <warns@pre-sense.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index 34ddda888e631e8ad338b1271a25efe10e93477d..9158c07b2bd55d986dbe4f50c07c485545623dc0 100644 (file)
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -469,17 +469,22 @@ befs_follow_link(struct dentry *dentry, struct nameidata *nd)
                befs_data_stream *data = &befs_ino->i_data.ds;
                befs_off_t len = data->size;
 
-               befs_debug(sb, "Follow long symlink");
-
-               link = kmalloc(len, GFP_NOFS);
-               if (!link) {
-                       link = ERR_PTR(-ENOMEM);
-               } else if (befs_read_lsymlink(sb, data, link, len) != len) {
-                       kfree(link);
-                       befs_error(sb, "Failed to read entire long symlink");
+               if (len == 0) {
+                       befs_error(sb, "Long symlink with illegal length");
                        link = ERR_PTR(-EIO);
                } else {
-                       link[len - 1] = '\0';
+                       befs_debug(sb, "Follow long symlink");
+
+                       link = kmalloc(len, GFP_NOFS);
+                       if (!link) {
+                               link = ERR_PTR(-ENOMEM);
+                       } else if (befs_read_lsymlink(sb, data, link, len) != len) {
+                               kfree(link);
+                               befs_error(sb, "Failed to read entire long symlink");
+                               link = ERR_PTR(-EIO);
+                       } else {
+                               link[len - 1] = '\0';
+                       }
                }
        } else {
                link = befs_ino->i_data.symlink;