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Message-id: <1437732285-11524-5-git-send-email-l.pawelczyk@samsung.com>
Date: Fri, 24 Jul 2015 12:04:38 +0200
From: Lukasz Pawelczyk <l.pawelczyk@...sung.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>,
"Serge E. Hallyn" <serge@...lyn.com>,
Al Viro <viro@...iv.linux.org.uk>,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...capital.net>,
Arnd Bergmann <arnd@...db.de>,
Casey Schaufler <casey@...aufler-ca.com>,
David Howells <dhowells@...hat.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Paris <eparis@...isplace.org>,
Fabian Frederick <fabf@...net.be>,
Greg KH <gregkh@...uxfoundation.org>,
James Morris <james.l.morris@...cle.com>,
Jiri Slaby <jslaby@...e.com>, Joe Perches <joe@...ches.com>,
John Johansen <john.johansen@...onical.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Lukasz Pawelczyk <l.pawelczyk@...sung.com>,
Mauro Carvalho Chehab <mchehab@....samsung.com>,
NeilBrown <neilb@...e.de>, Oleg Nesterov <oleg@...hat.com>,
Paul Moore <paul@...l-moore.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Zefan Li <lizefan@...wei.com>, linux-doc@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov
Cc: havner@...il.com
Subject: [PATCH v3 04/11] lsm: inode_pre_setxattr hook
Add a new LSM hook called before inode's setxattr. It is required for
LSM to be able to reliably replace the xattr's value to be set to
filesystem in __vfs_setxattr_noperm(). Useful for mapped values, like in
the upcoming Smack namespace patches.
Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@...sung.com>
---
fs/xattr.c | 10 ++++++++++
include/linux/lsm_hooks.h | 9 +++++++++
include/linux/security.h | 10 ++++++++++
security/security.c | 12 ++++++++++++
4 files changed, 41 insertions(+)
diff --git a/fs/xattr.c b/fs/xattr.c
index 072fee1..cbc8d19 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -100,12 +100,22 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
if (issec)
inode->i_flags &= ~S_NOSEC;
if (inode->i_op->setxattr) {
+ bool alloc = false;
+
+ error = security_inode_pre_setxattr(dentry, name, &value,
+ &size, flags, &alloc);
+ if (error)
+ return error;
+
error = inode->i_op->setxattr(dentry, name, value, size, flags);
if (!error) {
fsnotify_xattr(dentry);
security_inode_post_setxattr(dentry, name, value,
size, flags);
}
+
+ if (alloc)
+ kfree(value);
} else if (issec) {
const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
error = security_inode_setsecurity(inode, suffix, value,
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 1751864..0aeed91 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -349,6 +349,11 @@
* Check permission before setting the extended attributes
* @value identified by @name for @dentry.
* Return 0 if permission is granted.
+ * @inode_pre_setxattr:
+ * Be able to do some operation before setting the @value identified
+ * by @name on the filesystem. Replacing the @value and its @size is
+ * possible. Useful for mapped values. Set @alloc to true if @value
+ * needs to be kfreed afterwards.
* @inode_post_setxattr:
* Update inode security field after successful setxattr operation.
* @value identified by @name for @dentry.
@@ -1448,6 +1453,9 @@ union security_list_options {
int (*inode_getattr)(const struct path *path);
int (*inode_setxattr)(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags);
+ int (*inode_pre_setxattr)(struct dentry *dentry, const char *name,
+ const void **value, size_t *size,
+ int flags, bool *alloc);
void (*inode_post_setxattr)(struct dentry *dentry, const char *name,
const void *value, size_t size,
int flags);
@@ -1730,6 +1738,7 @@ struct security_hook_heads {
struct list_head inode_setattr;
struct list_head inode_getattr;
struct list_head inode_setxattr;
+ struct list_head inode_pre_setxattr;
struct list_head inode_post_setxattr;
struct list_head inode_getxattr;
struct list_head inode_listxattr;
diff --git a/include/linux/security.h b/include/linux/security.h
index f0d2914..24f91e0 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -263,6 +263,9 @@ int security_inode_setattr(struct dentry *dentry, struct iattr *attr);
int security_inode_getattr(const struct path *path);
int security_inode_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags);
+int security_inode_pre_setxattr(struct dentry *dentry, const char *name,
+ const void **value, size_t *size, int flags,
+ bool *alloc);
void security_inode_post_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags);
int security_inode_getxattr(struct dentry *dentry, const char *name);
@@ -691,6 +694,13 @@ static inline int security_inode_setxattr(struct dentry *dentry,
return cap_inode_setxattr(dentry, name, value, size, flags);
}
+static inline int security_inode_pre_setxattr(struct dentry *dentry,
+ const char *name, const void **value,
+ size_t *size, int flags, bool *alloc)
+{
+ return 0;
+}
+
static inline void security_inode_post_setxattr(struct dentry *dentry,
const char *name, const void *value, size_t size, int flags)
{ }
diff --git a/security/security.c b/security/security.c
index 88a3b78..e1d2c6f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -649,6 +649,16 @@ int security_inode_setxattr(struct dentry *dentry, const char *name,
return evm_inode_setxattr(dentry, name, value, size);
}
+int security_inode_pre_setxattr(struct dentry *dentry, const char *name,
+ const void **value, size_t *size, int flags,
+ bool *alloc)
+{
+ if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+ return 0;
+ return call_int_hook(inode_pre_setxattr, 0, dentry, name, value, size,
+ flags, alloc);
+}
+
void security_inode_post_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
@@ -1666,6 +1676,8 @@ struct security_hook_heads security_hook_heads = {
LIST_HEAD_INIT(security_hook_heads.inode_getattr),
.inode_setxattr =
LIST_HEAD_INIT(security_hook_heads.inode_setxattr),
+ .inode_pre_setxattr =
+ LIST_HEAD_INIT(security_hook_heads.inode_pre_setxattr),
.inode_post_setxattr =
LIST_HEAD_INIT(security_hook_heads.inode_post_setxattr),
.inode_getxattr =
--
2.4.3
--
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