orangefs: fix xattr related buffer overflow...

Willy Tarreau <w@1wt.eu> forwarded me a message from
Disclosure <disclosure@aisle.com> with the following
warning:

> The helper `xattr_key()` uses the pointer variable in the loop condition
> rather than dereferencing it. As `key` is incremented, it remains non-NULL
> (until it runs into unmapped memory), so the loop does not terminate on
> valid C strings and will walk memory indefinitely, consuming CPU or hanging
> the thread.

I easily reproduced this with setfattr and getfattr, causing a kernel
oops, hung user processes and corrupted orangefs files. Disclosure
sent along a diff (not a patch) with a suggested fix, which I based
this patch on.

After xattr_key started working right, xfstest generic/069 exposed an
xattr related memory leak that lead to OOM. xattr_key returns
a hashed key.  When adding xattrs to the orangefs xattr cache, orangefs
used hash_add, a kernel hashing macro. hash_add also hashes the key using
hash_log which resulted in additions to the xattr cache going to the wrong
hash bucket. generic/069 tortures a single file and orangefs does a
getattr for the xattr "security.capability" every time. Orangefs
negative caches on xattrs which includes a kmalloc. Since adds to the
xattr cache were going to the wrong bucket, every getattr for
"security.capability" resulted in another kmalloc, none of which were
ever freed.

I changed the two uses of hash_add to hlist_add_head instead
and the memory leak ceased and generic/069 quit throwing furniture.

Signed-off-by: Mike Marshall <hubcap@omnibond.com>
Reported-by: Stanislav Fort of Aisle Research <stanislav.fort@aisle.com>

diff --git a/fs/orangefs/xattr.c b/fs/orangefs/xattr.c
index 74ef75586f3845c72d448bf0b196fd9280190ea0..eee3c5ed1bbbb8472ddad28b4afedfe0501bdb5d 100644 (file)
--- a/fs/orangefs/xattr.c
+++ b/fs/orangefs/xattr.c
@@ -54,7 +54,9 @@ static inline int convert_to_internal_xattr_flags(int setxattr_flags)
 static unsigned int xattr_key(const char *key)
 {
        unsigned int i = 0;
-       while (key)
+       if (!key)
+               return 0;
+       while (*key)
                i += *key++;
        return i % 16;
 }
@@ -175,8 +177,8 @@ ssize_t orangefs_inode_getxattr(struct inode *inode, const char *name,
                                cx->length = -1;
                                cx->timeout = jiffies +
                                    orangefs_getattr_timeout_msecs*HZ/1000;
-                               hash_add(orangefs_inode->xattr_cache, &cx->node,
-                                   xattr_key(cx->key));
+                               hlist_add_head( &cx->node,
+                                   &orangefs_inode->xattr_cache[xattr_key(cx->key)]);
                        }
                }
                goto out_release_op;
@@ -229,8 +231,8 @@ ssize_t orangefs_inode_getxattr(struct inode *inode, const char *name,
                        memcpy(cx->val, buffer, length);
                        cx->length = length;
                        cx->timeout = jiffies + HZ;
-                       hash_add(orangefs_inode->xattr_cache, &cx->node,
-                           xattr_key(cx->key));
+                       hlist_add_head(&cx->node,
+                               &orangefs_inode->xattr_cache[xattr_key(cx->key)]);
                }
        }