On 7/19/2024 10:08 AM, Paul Moore wrote:
On Jul 11, 2024 Xu Kuohai <xukuohai@xxxxxxxxxxxxxxx> wrote:
To be consistent with most LSM hooks, convert the return value of
hook inode_listsecurity to 0 or a negative error code.
Before:
- Hook inode_listsecurity returns number of bytes used/required on
success or a negative error code on failure.
After:
- Hook inode_listsecurity returns 0 on success or a negative error
code on failure. An output parameter @bytes is introduced to hold
the number of bytes used/required on success.
Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 5 ++++-
fs/xattr.c | 5 ++++-
include/linux/lsm_hook_defs.h | 2 +-
include/linux/security.h | 7 ++++---
net/socket.c | 9 +++++----
security/security.c | 29 +++++++++++++++++++++++++----
security/selinux/hooks.c | 8 +++++---
security/smack/smack_lsm.c | 6 ++++--
8 files changed, 52 insertions(+), 19 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a691fa10b3e9..6d75758ba3d5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7848,10 +7848,13 @@ static int nfs4_xattr_get_nfs4_label(const struct xattr_handler *handler,
static ssize_t
nfs4_listxattr_nfs4_label(struct inode *inode, char *list, size_t list_len)
{
+ size_t bytes;
int len = 0;
if (nfs_server_capable(inode, NFS_CAP_SECURITY_LABEL)) {
- len = security_inode_listsecurity(inode, list, list_len);
+ len = security_inode_listsecurity(inode, list, list_len, &bytes);
+ if (!len)
+ len = bytes;
if (len >= 0 && list_len && len > list_len)
return -ERANGE;
}
See my comments below.
diff --git a/fs/xattr.c b/fs/xattr.c
index f4e3bedf7272..ab7d7123a016 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -485,6 +485,7 @@ vfs_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct inode *inode = d_inode(dentry);
ssize_t error;
+ size_t bytes;
error = security_inode_listxattr(dentry);
if (error)
@@ -493,7 +494,9 @@ vfs_listxattr(struct dentry *dentry, char *list, size_t size)
if (inode->i_op->listxattr) {
error = inode->i_op->listxattr(dentry, list, size);
} else {
- error = security_inode_listsecurity(inode, list, size);
+ error = security_inode_listsecurity(inode, list, size, &bytes);
+ if (!error)
+ error = bytes;
if (size && error > size)
error = -ERANGE;
More on this below, but since the buffer length is fixed we are
already going to have to do a length comparison in the LSMs, why not
do the check and return -ERANGE there?
Sounds great, thanks
diff --git a/net/socket.c b/net/socket.c
index e416920e9399..43f0e3c9a6e0 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -571,12 +571,13 @@ static struct socket *sockfd_lookup_light(int fd, int *err, int *fput_needed)
static ssize_t sockfs_listxattr(struct dentry *dentry, char *buffer,
size_t size)
{
- ssize_t len;
+ int err;
+ size_t len;
ssize_t used = 0;
- len = security_inode_listsecurity(d_inode(dentry), buffer, size);
- if (len < 0)
- return len;
+ err = security_inode_listsecurity(d_inode(dentry), buffer, size, &len);
+ if (err < 0)
+ return err;
used += len;
if (buffer) {
if (size < used)
It doesn't show in the patch/diff, but if the LSM hook handles the length
comparison we can simplify the -ERANGE code in sockfs_listxattr().
Will do
diff --git a/security/security.c b/security/security.c
index 614f14cbfff7..26eea8f4cd74 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2597,20 +2597,41 @@ int security_inode_setsecurity(struct inode *inode, const char *name,
* @inode: inode
* @buffer: buffer
* @buffer_size: size of buffer
+ * @bytes: number of bytes used/required
*
* Copy the extended attribute names for the security labels associated with
* @inode into @buffer. The maximum size of @buffer is specified by
* @buffer_size. @buffer may be NULL to request the size of the buffer
* required.
*
- * Return: Returns number of bytes used/required on success.
+ * Return: Returns 0 on success or a negative error code on failure.
*/
int security_inode_listsecurity(struct inode *inode,
- char *buffer, size_t buffer_size)
+ char *buffer, size_t buffer_size,
+ size_t *bytes)
{
+ int rc;
+ size_t used;
+ struct security_hook_list *hp;
+
if (unlikely(IS_PRIVATE(inode)))
- return 0;
- return call_int_hook(inode_listsecurity, inode, buffer, buffer_size);
+ return *bytes = 0;
+
+ used = 0;
+ hlist_for_each_entry(hp, &security_hook_heads.inode_listsecurity,
+ list) {
+ rc = hp->hook.inode_listsecurity(inode, buffer, buffer_size,
+ &used);
+ if (rc < 0)
+ return rc;
+ if (used != 0)
+ break;
+ }
+
+ *bytes = used;
+
+ return 0;
+
}
EXPORT_SYMBOL(security_inode_listsecurity);
For reasons associated with the static_call work, we really need to
limit ourselves to the call_{int,void}_hook() macros on any new code.
The good news is that I think we can do that here as the existing
code isn't multi-LSM friendly.
Thanks for pointing that out. Good to know the current code is acceptable.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 70792bba24d9..5dedd3917d57 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3481,16 +3481,18 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name,
return 0;
}
-static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
+static int selinux_inode_listsecurity(struct inode *inode, char *buffer,
+ size_t buffer_size, size_t *bytes)
{
const int len = sizeof(XATTR_NAME_SELINUX);
if (!selinux_initialized())
- return 0;
+ return *bytes = 0;
if (buffer && len <= buffer_size)
memcpy(buffer, XATTR_NAME_SELINUX, len);
- return len;
+ *bytes = len;
+ return 0;
}
Let's do something like below so we can catch -ERANGE in the LSMs
themselves.
if (!selinux_initialized())
return *bytes = 0;
*bytes = sizeof(XATTR_NAME_SELINUX);
if (len > buffer_size);
return -ERANGE;
if (buffer)
memcpy(buffer, XATTR_NAME_SELINUX, *bytes);
return 0;
Will do
static void selinux_inode_getsecid(struct inode *inode, u32 *secid)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index e7a5f6fd9a2d..6f73906bf7ea 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1611,16 +1611,18 @@ static int smack_inode_getsecurity(struct mnt_idmap *idmap,
* @inode: the object
* @buffer: where they go
* @buffer_size: size of buffer
+ * @bytes: number of data bytes in buffer
*/
static int smack_inode_listsecurity(struct inode *inode, char *buffer,
- size_t buffer_size)
+ size_t buffer_size, size_t *bytes)
{
int len = sizeof(XATTR_NAME_SMACK);
if (buffer != NULL && len <= buffer_size)
memcpy(buffer, XATTR_NAME_SMACK, len);
- return len;
+ *bytes = len;
+ return 0;
}
A similar approach could be used here.
Will do
--
paul-moore.com
