[PATCH 3.14 07/92] btrfs: dont accept bare namespace as a valid xattr

Greg Kroah-Hartman
2015-05-02T19:42:07Z

From: David Sterba <dsterba@suse.cz>

commit 3c3b04d10ff1811a27f86684ccd2f5ba6983211d upstream.

Due to insufficient check in btrfs_is_valid_xattr, this unexpectedly
works:

$ touch file
$ setfattr -n user. -v 1 file
$ getfattr -d file
user.="1"

ie. the missing attribute name after the namespace.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=94291
Reported-by: William Douglas <william.douglas@intel.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/xattr.c | 53 +++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 39 insertions(+), 14 deletions(-)

--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -324,22 +324,42 @@ const struct xattr_handler *btrfs_xattr_
/*
* Check if the attribute is in a supported namespace.
*
- * This applied after the check for the synthetic attributes in the system
+ * This is applied after the check for the synthetic attributes in the system
* namespace.
*/
-static bool btrfs_is_valid_xattr(const char *name)
+static int btrfs_is_valid_xattr(const char *name)
{
- return !strncmp(name, XATTR_SECURITY_PREFIX,
- XATTR_SECURITY_PREFIX_LEN) ||
- !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
- !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
- !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) ||
- !strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN);
+ int len = strlen(name);
+ int prefixlen = 0;
+
+ if (!strncmp(name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN))
+ prefixlen = XATTR_SECURITY_PREFIX_LEN;
+ else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ prefixlen = XATTR_SYSTEM_PREFIX_LEN;
+ else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+ prefixlen = XATTR_TRUSTED_PREFIX_LEN;
+ else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
+ prefixlen = XATTR_USER_PREFIX_LEN;
+ else if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
+ prefixlen = XATTR_BTRFS_PREFIX_LEN;
+ else
+ return -EOPNOTSUPP;
+
+ /*
+ * The name cannot consist of just prefix
+ */
+ if (len <= prefixlen)
+ return -EINVAL;
+
+ return 0;
}

ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
void *buffer, size_t size)
{
+ int ret;
+
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler
@@ -348,8 +368,9 @@ ssize_t btrfs_getxattr(struct dentry *de
if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
return generic_getxattr(dentry, name, buffer, size);

- if (!btrfs_is_valid_xattr(name))
- return -EOPNOTSUPP;
+ ret = btrfs_is_valid_xattr(name);
+ if (ret)
+ return ret;
return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
}

@@ -357,6 +378,7 @@ int btrfs_setxattr(struct dentry *dentry
size_t size, int flags)
{
struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+ int ret;

/*
* The permission on security.* and system.* is not checked
@@ -373,8 +395,9 @@ int btrfs_setxattr(struct dentry *dentry
if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
return generic_setxattr(dentry, name, value, size, flags);

- if (!btrfs_is_valid_xattr(name))
- return -EOPNOTSUPP;
+ ret = btrfs_is_valid_xattr(name);
+ if (ret)
+ return ret;

if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
return btrfs_set_prop(dentry->d_inode, name,
@@ -390,6 +413,7 @@ int btrfs_setxattr(struct dentry *dentry
int btrfs_removexattr(struct dentry *dentry, const char *name)
{
struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+ int ret;

/*
* The permission on security.* and system.* is not checked
@@ -406,8 +430,9 @@ int btrfs_removexattr(struct dentry *den
if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
return generic_removexattr(dentry, name);

- if (!btrfs_is_valid_xattr(name))
- return -EOPNOTSUPP;
+ ret = btrfs_is_valid_xattr(name);
+ if (ret)
+ return ret;

if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
return btrfs_set_prop(dentry->d_inode, name,