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From 7cb35119d067191ce9ebc380a599db0b03cbd9d9 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 1 Sep 2016 11:12:00 +0200
Subject: [PATCH] ovl: listxattr: use strnlen()
Be defensive about what underlying fs provides us in the returned xattr
list buffer. If it's not properly null terminated, bail out with a warning
insead of BUG.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
---
fs/overlayfs/inode.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -277,7 +277,8 @@ ssize_t ovl_listxattr(struct dentry *den
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
ssize_t res;
- int off;
+ size_t len;
+ char *s;
res = vfs_listxattr(realpath.dentry, list, size);
if (res <= 0 || size == 0)
@@ -287,17 +288,19 @@ ssize_t ovl_listxattr(struct dentry *den
return res;
/* filter out private xattrs */
- for (off = 0; off < res;) {
- char *s = list + off;
- size_t slen = strlen(s) + 1;
+ for (s = list, len = res; len;) {
+ size_t slen = strnlen(s, len) + 1;
- BUG_ON(off + slen > res);
+ /* underlying fs providing us with an broken xattr list? */
+ if (WARN_ON(slen > len))
+ return -EIO;
+ len -= slen;
if (ovl_is_private_xattr(s)) {
res -= slen;
- memmove(s, s + slen, res - off);
+ memmove(s, s + slen, len);
} else {
- off += slen;
+ s += slen;
}
}
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