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Subject[TOMOYO #13 (mmotm 2008-11-19-02-19) 01/11] Introduce security_path_clear() hook.
To perform DAC performed in vfs_foo() before MAC, we let security_path_foo()
save a result into our own hash table and return 0, and let security_inode_foo()
return the saved result. Since security_inode_foo() is not always called after
security_path_foo(), we need security_path_clear() to clear the hash table.

Signed-off-by: Kentaro Takeda <takedakn@nttdata.co.jp>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Toshiharu Harada <haradats@nttdata.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Crispin Cowan <crispin@crispincowan.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

fs/namei.c | 9 +++++++++
fs/open.c | 2 ++
include/linux/security.h | 12 ++++++++++++
net/unix/af_unix.c | 1 +
security/capability.c | 5 +++++
security/security.c | 6 ++++++
6 files changed, 35 insertions(+)

--- linux-2.6.28-rc5-mm1.orig/fs/namei.c
+++ linux-2.6.28-rc5-mm1/fs/namei.c
@@ -1566,6 +1566,7 @@ int may_open(struct nameidata *nd, int a
error = do_truncate(dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
NULL);
+ security_path_clear();
}
put_write_access(inode);
if (error)
@@ -1594,6 +1595,7 @@ static int __open_namei_create(struct na
if (error)
goto out_unlock;
error = vfs_create(dir->d_inode, path->dentry, mode, nd);
+ security_path_clear();
out_unlock:
mutex_unlock(&dir->d_inode->i_mutex);
dput(nd->path.dentry);
@@ -2022,6 +2024,7 @@ asmlinkage long sys_mknodat(int dfd, con
error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
break;
}
+ security_path_clear();
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
@@ -2086,6 +2089,7 @@ asmlinkage long sys_mkdirat(int dfd, con
if (error)
goto out_drop_write;
error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
+ security_path_clear();
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
@@ -2200,6 +2204,7 @@ static long do_rmdir(int dfd, const char
if (error)
goto exit4;
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
+ security_path_clear();
exit4:
mnt_drop_write(nd.path.mnt);
exit3:
@@ -2289,6 +2294,7 @@ static long do_unlinkat(int dfd, const c
if (error)
goto exit3;
error = vfs_unlink(nd.path.dentry->d_inode, dentry);
+ security_path_clear();
exit3:
mnt_drop_write(nd.path.mnt);
exit2:
@@ -2374,6 +2380,7 @@ asmlinkage long sys_symlinkat(const char
if (error)
goto out_drop_write;
error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
+ security_path_clear();
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
@@ -2475,6 +2482,7 @@ asmlinkage long sys_linkat(int olddfd, c
if (error)
goto out_drop_write;
error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
+ security_path_clear();
out_drop_write:
mnt_drop_write(nd.path.mnt);
out_dput:
@@ -2715,6 +2723,7 @@ asmlinkage long sys_renameat(int olddfd,
goto exit6;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
+ security_path_clear();
exit6:
mnt_drop_write(oldnd.path.mnt);
exit5:
--- linux-2.6.28-rc5-mm1.orig/fs/open.c
+++ linux-2.6.28-rc5-mm1/fs/open.c
@@ -277,6 +277,7 @@ static long do_sys_truncate(const char _
if (!error) {
DQUOT_INIT(inode);
error = do_truncate(path.dentry, length, 0, NULL);
+ security_path_clear();
}

put_write_and_out:
@@ -335,6 +336,7 @@ static long do_sys_ftruncate(unsigned in
ATTR_MTIME|ATTR_CTIME, file);
if (!error)
error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
+ security_path_clear();
out_putf:
fput(file);
out:
--- linux-2.6.28-rc5-mm1.orig/include/linux/security.h
+++ linux-2.6.28-rc5-mm1/include/linux/security.h
@@ -527,6 +527,12 @@ static inline void security_free_mnt_opt
* @inode contains a pointer to the inode.
* @secid contains a pointer to the location where result will be saved.
* In case of failure, @secid will be set to zero.
+ * @path_clear:
+ * Clear error code stored by security_path_*() in case
+ * security_inode_*() was not called when DAC returned an error.
+ * This hook allows LSM modules which use security_path_*() defer
+ * returning LSM's error code till security_inode_*() is called so that
+ * DAC's error (if any) is returned to the caller instead of LSM's error.
*
* Security hooks for file operations
*
@@ -1402,6 +1408,7 @@ struct security_operations {
struct dentry *new_dentry);
int (*path_rename) (struct path *old_dir, struct dentry *old_dentry,
struct path *new_dir, struct dentry *new_dentry);
+ void (*path_clear) (void);
#endif

int (*inode_alloc_security) (struct inode *inode);
@@ -2792,6 +2799,7 @@ int security_path_link(struct dentry *ol
struct dentry *new_dentry);
int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
struct path *new_dir, struct dentry *new_dentry);
+void security_path_clear(void);
#else /* CONFIG_SECURITY_PATH */
static inline int security_path_unlink(struct path *dir, struct dentry *dentry)
{
@@ -2842,6 +2850,10 @@ static inline int security_path_rename(s
{
return 0;
}
+
+static inline void security_path_clear(void)
+{
+}
#endif /* CONFIG_SECURITY_PATH */

#ifdef CONFIG_KEYS
--- linux-2.6.28-rc5-mm1.orig/net/unix/af_unix.c
+++ linux-2.6.28-rc5-mm1/net/unix/af_unix.c
@@ -832,6 +832,7 @@ static int unix_bind(struct socket *sock
if (err)
goto out_mknod_drop_write;
err = vfs_mknod(nd.path.dentry->d_inode, dentry, mode, 0);
+ security_path_clear();
out_mknod_drop_write:
mnt_drop_write(nd.path.mnt);
if (err)
--- linux-2.6.28-rc5-mm1.orig/security/capability.c
+++ linux-2.6.28-rc5-mm1/security/capability.c
@@ -308,6 +308,10 @@ static int cap_path_truncate(struct path
{
return 0;
}
+
+static void cap_path_clear(void)
+{
+}
#endif

static int cap_file_permission(struct file *file, int mask)
@@ -939,6 +943,7 @@ void security_fixup_ops(struct security_
set_to_cap_if_null(ops, path_link);
set_to_cap_if_null(ops, path_rename);
set_to_cap_if_null(ops, path_truncate);
+ set_to_cap_if_null(ops, path_clear);
#endif
set_to_cap_if_null(ops, file_permission);
set_to_cap_if_null(ops, file_alloc_security);
--- linux-2.6.28-rc5-mm1.orig/security/security.c
+++ linux-2.6.28-rc5-mm1/security/security.c
@@ -419,6 +419,12 @@ int security_path_truncate(struct path *
return 0;
return security_ops->path_truncate(path, length, time_attrs, filp);
}
+
+void security_path_clear(void)
+{
+ return security_ops->path_clear();
+}
+EXPORT_SYMBOL(security_path_clear);
#endif

int security_inode_create(struct inode *dir, struct dentry *dentry, int mode)
--


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