befs: Validate length of long symbolic links.

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

fs/befs/linuxvfs.c

@@ -474,6 +474,10 @@ befs_follow_link(struct dentry *dentry, struct nameidata *nd)
 		befs_data_stream *data = &befs_ino->i_data.ds;
 		befs_off_t len = data->size;
 
+		if (len == 0) {
+			befs_error(sb, "Long symlink with illegal length");
+			link = ERR_PTR(-EIO);
+		} else {
 			befs_debug(sb, "Follow long symlink");
 
 			link = kmalloc(len, GFP_NOFS);
@@ -486,6 +490,7 @@ befs_follow_link(struct dentry *dentry, struct nameidata *nd)
 			} else {
 				link[len - 1] = '\0';
 			}
+		}
 	} else {
 		link = befs_ino->i_data.symlink;
 	}