When executing a setuid binary the kernel will verify in bprm_fill_uid()
that the inode has a mapping in the caller's user namespace before
setting the callers uid and gid. Let bprm_fill_uid() handle idmapped
mounts. If the inode is accessed through an idmapped mount it is mapped
according to the mount's user namespace. Afterwards the checks are
identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
/* v2 */
unchanged
/* v3 */
unchanged
/* v4 */
- Serge Hallyn <serge@xxxxxxxxxx>:
- Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
terminology consistent.
/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837
---
fs/exec.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 36a1b927a8ae..61ae826d5a16 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1580,6 +1580,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
{
/* Handle suid and sgid on files */
+ struct user_namespace *mnt_userns;
struct inode *inode;
unsigned int mode;
kuid_t uid;
@@ -1596,13 +1597,15 @@ static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
if (!(mode & (S_ISUID|S_ISGID)))
return;
+ mnt_userns = mnt_user_ns(file->f_path.mnt);
+
/* Be careful if suid/sgid is set */
inode_lock(inode);
/* reload atomically mode/uid/gid now that lock held */
mode = inode->i_mode;
- uid = inode->i_uid;
- gid = inode->i_gid;
+ uid = i_uid_into_mnt(mnt_userns, inode);
+ gid = i_gid_into_mnt(mnt_userns, inode);
inode_unlock(inode);
/* We ignore suid/sgid if there are no mappings for them in the ns */
--
2.30.0
