From: Christian Brauner <christian.brauner@xxxxxxxxxx>
commit 476860b3eb4a50958243158861d5340066df5af2 upstream.
If the caller's fs{g,u}id aren't mapped in the mount's idmapping we can
return early and skip the check whether the mapped fs{g,u}id also have a
mapping in the filesystem's idmapping. If the fs{g,u}id aren't mapped in
the mount's idmapping they consequently can't be mapped in the
filesystem's idmapping. So there's no point in checking that.
Link: https://lore.kernel.org/r/20211123114227.3124056-4-brauner@xxxxxxxxxx (v1)
Link: https://lore.kernel.org/r/20211130121032.3753852-4-brauner@xxxxxxxxxx (v2)
Link: https://lore.kernel.org/r/20211203111707.3901969-4-brauner@xxxxxxxxxx
Cc: Seth Forshee <sforshee@xxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: linux-fsdevel@xxxxxxxxxxxxxxx
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
Reviewed-by: Seth Forshee <sforshee@xxxxxxxxxxxxxxxx>
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/fs.h | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1697,10 +1697,18 @@ static inline void inode_fsgid_set(struc
static inline bool fsuidgid_has_mapping(struct super_block *sb,
struct user_namespace *mnt_userns)
{
- struct user_namespace *s_user_ns = sb->s_user_ns;
+ struct user_namespace *fs_userns = sb->s_user_ns;
+ kuid_t kuid;
+ kgid_t kgid;
- return kuid_has_mapping(s_user_ns, mapped_fsuid(mnt_userns)) &&
- kgid_has_mapping(s_user_ns, mapped_fsgid(mnt_userns));
+ kuid = mapped_fsuid(mnt_userns);
+ if (!uid_valid(kuid))
+ return false;
+ kgid = mapped_fsgid(mnt_userns);
+ if (!gid_valid(kgid))
+ return false;
+ return kuid_has_mapping(fs_userns, kuid) &&
+ kgid_has_mapping(fs_userns, kgid);
}
extern struct timespec64 current_time(struct inode *inode);
