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Subject[035/111] jfs: dont allow os2 xattr namespace overlap with others
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>

commit aca0fa34bdaba39bfddddba8ca70dba4782e8fe6 upstream.
It's currently possible to bypass xattr namespace access rules by
prefixing valid xattr names with "os2.", since the os2 namespace stores
extended attributes in a legacy format with no prefix.

This patch adds checking to deny access to any valid namespace prefix
following "os2.".

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Reported-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/jfs/xattr.c | 87 ++++++++++++++++++++++++---------------------------------
1 file changed, 38 insertions(+), 49 deletions(-)
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -85,46 +85,25 @@ struct ea_buffer {
#define EA_MALLOC 0x0008


+static int is_known_namespace(const char *name)
+{
+ if (strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) &&
+ strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) &&
+ strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) &&
+ strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+ return false;
+
+ return true;
+}
+
/*
* These three routines are used to recognize on-disk extended attributes
* that are in a recognized namespace. If the attribute is not recognized,
* "os2." is prepended to the name
*/
-static inline int is_os2_xattr(struct jfs_ea *ea)
+static int is_os2_xattr(struct jfs_ea *ea)
{
- /*
- * Check for "system."
- */
- if ((ea->namelen >= XATTR_SYSTEM_PREFIX_LEN) &&
- !strncmp(ea->name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
- return false;
- /*
- * Check for "user."
- */
- if ((ea->namelen >= XATTR_USER_PREFIX_LEN) &&
- !strncmp(ea->name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
- return false;
- /*
- * Check for "security."
- */
- if ((ea->namelen >= XATTR_SECURITY_PREFIX_LEN) &&
- !strncmp(ea->name, XATTR_SECURITY_PREFIX,
- XATTR_SECURITY_PREFIX_LEN))
- return false;
- /*
- * Check for "trusted."
- */
- if ((ea->namelen >= XATTR_TRUSTED_PREFIX_LEN) &&
- !strncmp(ea->name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
- return false;
- /*
- * Add any other valid namespace prefixes here
- */
-
- /*
- * We assume it's OS/2's flat namespace
- */
- return true;
+ return !is_known_namespace(ea->name);
}

static inline int name_size(struct jfs_ea *ea)
@@ -762,13 +741,23 @@ static int can_set_xattr(struct inode *i
if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
return can_set_system_xattr(inode, name, value, value_len);

+ if (!strncmp(name, XATTR_OS2_PREFIX, XATTR_OS2_PREFIX_LEN)) {
+ /*
+ * This makes sure that we aren't trying to set an
+ * attribute in a different namespace by prefixing it
+ * with "os2."
+ */
+ if (is_known_namespace(name + XATTR_OS2_PREFIX_LEN))
+ return -EOPNOTSUPP;
+ return 0;
+ }
+
/*
* Don't allow setting an attribute in an unknown namespace.
*/
if (strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) &&
strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) &&
- strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) &&
- strncmp(name, XATTR_OS2_PREFIX, XATTR_OS2_PREFIX_LEN))
+ strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
return -EOPNOTSUPP;

return 0;
@@ -950,19 +939,8 @@ ssize_t __jfs_getxattr(struct inode *ino
int xattr_size;
ssize_t size;
int namelen = strlen(name);
- char *os2name = NULL;
char *value;

- if (strncmp(name, XATTR_OS2_PREFIX, XATTR_OS2_PREFIX_LEN) == 0) {
- os2name = kmalloc(namelen - XATTR_OS2_PREFIX_LEN + 1,
- GFP_KERNEL);
- if (!os2name)
- return -ENOMEM;
- strcpy(os2name, name + XATTR_OS2_PREFIX_LEN);
- name = os2name;
- namelen -= XATTR_OS2_PREFIX_LEN;
- }
-
down_read(&JFS_IP(inode)->xattr_sem);

xattr_size = ea_get(inode, &ea_buf, 0);
@@ -1000,8 +978,6 @@ ssize_t __jfs_getxattr(struct inode *ino
out:
up_read(&JFS_IP(inode)->xattr_sem);

- kfree(os2name);
-
return size;
}

@@ -1010,6 +986,19 @@ ssize_t jfs_getxattr(struct dentry *dent
{
int err;

+ if (strncmp(name, XATTR_OS2_PREFIX, XATTR_OS2_PREFIX_LEN) == 0) {
+ /*
+ * skip past "os2." prefix
+ */
+ name += XATTR_OS2_PREFIX_LEN;
+ /*
+ * Don't allow retrieving properly prefixed attributes
+ * by prepending them with "os2."
+ */
+ if (is_known_namespace(name))
+ return -EOPNOTSUPP;
+ }
+
err = __jfs_getxattr(dentry->d_inode, name, data, buf_size);

return err;



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