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VFS: Reorder vfs_getxattr to avoid unnecessary calls to the LSM 

Originally vfs_getxattr would pull the security xattr variable using
the inode getxattr handle and then proceed to clobber it with a subsequent call
to the LSM.

This patch reorders the two operations such that when the xattr requested is
in the security namespace it first attempts to grab the value from the LSM
directly.

If it fails to obtain the value because there is no module present or the
module does not support the operation it will fall back to using the inode
getxattr operation.

In the event that both are inaccessible it returns EOPNOTSUPP.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David P. Quigley 2008-02-04 22:29:40 -08:00 committed by Linus Torvalds
parent 4249259404
commit 4bea58053f
1 changed files with 8 additions and 7 deletions
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15
fs/xattr.c
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@ -145,11 +145,6 @@ vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
if (error)
return error;
if (inode->i_op->getxattr)
error = inode->i_op->getxattr(dentry, name, value, size);
else
error = -EOPNOTSUPP;
if (!strncmp(name, XATTR_SECURITY_PREFIX,
XATTR_SECURITY_PREFIX_LEN)) {
const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
@ -158,9 +153,15 @@ vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
* Only overwrite the return value if a security module
* is actually active.
*/
if (ret != -EOPNOTSUPP)
error = ret;
if (ret == -EOPNOTSUPP)
goto nolsm;
return ret;
}
nolsm:
if (inode->i_op->getxattr)
error = inode->i_op->getxattr(dentry, name, value, size);
else
error = -EOPNOTSUPP;
return error;
}