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> --- include/linux/fs.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index b1d446d71c3f..ffc06557618c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1697,10 +1697,18 @@ static inline void inode_fsgid_set(struct inode *inode, 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); -- 2.34.1