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evm: fix potential race when removing xattrs

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EVM needs to be atomically updated when removing xattrs.
Otherwise concurrent EVM verification may fail in between.
This patch fixes by moving i_mutex unlocking after calling
EVM hook. fsnotify_xattr() is also now called while locked
the same way as it is done in __vfs_setxattr_noperm.

Changelog:
- remove unused 'inode' variable.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
This commit is contained in:
Dmitry Kasatkin 2014-11-20 16:31:01 +02:00 committed by Mimi Zohar
parent 5101a1850b
commit 7c51bb00c4
2 changed files with 8 additions and 9 deletions
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10
fs/xattr.c
View File

@ -298,18 +298,18 @@ vfs_removexattr(struct dentry *dentry, const char *name)
mutex_lock(&inode->i_mutex); mutex_lock(&inode->i_mutex);
error = security_inode_removexattr(dentry, name); error = security_inode_removexattr(dentry, name);
if (error) { if (error)
mutex_unlock(&inode->i_mutex); goto out;
return error;
}
error = inode->i_op->removexattr(dentry, name); error = inode->i_op->removexattr(dentry, name);
mutex_unlock(&inode->i_mutex);
if (!error) { if (!error) {
fsnotify_xattr(dentry); fsnotify_xattr(dentry);
evm_inode_post_removexattr(dentry, name); evm_inode_post_removexattr(dentry, name);
} }
out:
mutex_unlock(&inode->i_mutex);
return error; return error;
} }
EXPORT_SYMBOL_GPL(vfs_removexattr); EXPORT_SYMBOL_GPL(vfs_removexattr);

7
security/integrity/evm/evm_main.c
View File

@ -387,17 +387,16 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
* @xattr_name: pointer to the affected extended attribute name * @xattr_name: pointer to the affected extended attribute name
* *
* Update the HMAC stored in 'security.evm' to reflect removal of the xattr. * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
*
* No need to take the i_mutex lock here, as this function is called from
* vfs_removexattr() which takes the i_mutex.
*/ */
void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
{ {
struct inode *inode = d_backing_inode(dentry);
if (!evm_initialized || !evm_protected_xattr(xattr_name)) if (!evm_initialized || !evm_protected_xattr(xattr_name))
return; return;
mutex_lock(&inode->i_mutex);
evm_update_evmxattr(dentry, xattr_name, NULL, 0); evm_update_evmxattr(dentry, xattr_name, NULL, 0);
mutex_unlock(&inode->i_mutex);
} }
/** /**