Commit 025e8807 authored by Mike Marshall's avatar Mike Marshall
Browse files

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: default avatarMike Marshall <hubcap@omnibond.com>
Reported-by: default avatarStanislav Fort of Aisle Research <stanislav.fort@aisle.com>
parent 3dffadfa

fs/orangefs/xattr.c

+7 −5
Original line number Diff line number Diff line
@@ -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)]);

		}

	}