Re: [PATCH v23 20/22] vfs: Add richacl permission checking

Andreas Gruenbacher
2016-07-14T22:38:35Z

On Tue, Jul 12, 2016 at 2:13 PM, Jeff Layton <jlayton@redhat.com> wrote:
> On Thu, 2016-06-30 at 15:47 +0200, Andreas Gruenbacher wrote:
>> Hook the richacl permission checking function into the vfs.
>>
>> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
>> ---
>> fs/namei.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 52 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/namei.c b/fs/namei.c
>> index 7a822d0..48c9958 100644
>> --- a/fs/namei.c
>> +++ b/fs/namei.c
>> @@ -34,6 +34,7 @@
>> #include
>> #include
>> #include
>> +#include
>> #include
>> #include
>> #include
>> @@ -256,7 +257,43 @@ void putname(struct filename *name)
>> __putname(name);
>> }
>>
>> -static int check_acl(struct inode *inode, int mask)
>> +static int check_richacl(struct inode *inode, int mask)
>> +{
>> +#ifdef CONFIG_FS_RICHACL
>> + if (mask & MAY_NOT_BLOCK) {
>> + struct base_acl *base_acl;
>> +
>> + base_acl = rcu_dereference(inode->i_acl);
>> + if (!base_acl)
>> + goto no_acl;
>> + /* no ->get_richacl() calls in RCU mode... */
>> + if (is_uncached_acl(base_acl))
>> + return -ECHILD;
>> + return richacl_permission(inode, richacl(base_acl),
>> + mask & ~MAY_NOT_BLOCK);
>> + } else {
>> + struct richacl *acl;
>> +
>> + acl = get_richacl(inode);
>> + if (IS_ERR(acl))
>> + return PTR_ERR(acl);
>> + if (acl) {
>> + int error = richacl_permission(inode, acl, mask);
>> + richacl_put(acl);
>> + return error;
>> + }
>> + }
>> +no_acl:
>> +#endif
>
> nit: Can you move the above to a static inline or something that becomes a noop when the config var is turned off?

We could move check_richacl into richacl.c and check_posix_acl into
posix_acl.c. Given that those functions are currently only called once
in namei.c, that's a very small improvement at most though.

>> + if (mask & (MAY_DELETE_SELF | MAY_TAKE_OWNERSHIP |
>> + MAY_CHMOD | MAY_SET_TIMES)) {
>> + /* File permission bits cannot grant this. */
>> + return -EACCES;
>> + }
>> + return -EAGAIN;
>> +}
>> +
>> +static int check_posix_acl(struct inode *inode, int mask)
>> {
>> #ifdef CONFIG_FS_POSIX_ACL
>> if (mask & MAY_NOT_BLOCK) {
>> @@ -294,11 +331,24 @@ static int acl_permission_check(struct inode *inode, int mask)
>> {
>> unsigned int mode = inode->i_mode;
>>
>> + /*
>> + * With POSIX ACLs, the (mode & S_IRWXU) bits exactly match the owner
>> + * permissions, and we can skip checking posix acls for the owner.
>> + * With richacls, the owner may be granted fewer permissions than the
>> + * mode bits seem to suggest (for example, append but not write), and
>> + * we always need to check the richacl.
>> + */
>> +
>> + if (IS_RICHACL(inode)) {
>> + int error = check_richacl(inode, mask);
>> + if (error != -EAGAIN)
>> + return error;
>> + }
>> if (likely(uid_eq(current_fsuid(), inode->i_uid)))
>> mode >>= 6;
>> else {
>> if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
>> - int error = check_acl(inode, mask);
>> + int error = check_posix_acl(inode, mask);
>> if (error != -EAGAIN)
>> return error;
>> }
>
> Looks fine other than the nit above:
>
> Reviewed-by: Jeff Layton <jlayton@redhat.com>

Thanks,
Andreas