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fs: tweak fsuidgid_has_mapping()

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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@kernel.org (v1)
Link: https://lore.kernel.org/r/20211130121032.3753852-4-brauner@kernel.org (v2)
Link: https://lore.kernel.org/r/20211203111707.3901969-4-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2021-12-03 12:17:00 +01:00
parent a793d79ea3
commit 476860b3eb
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
1 changed files with 11 additions and 3 deletions
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14
include/linux/fs.h
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@ -1695,10 +1695,18 @@ 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);