[v6,22/40] would_dump: handle idmapped mounts

Commit Message

Christian Brauner Jan. 21, 2021, 1:19 p.m. UTC

When determining whether or not to create a coredump the vfs will verify
that the caller is privileged over the inode. Make the would_dump()
helper handle idmapped mounts by passing down the mount's user namespace
of the exec file. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/[e-mail]
Cc: Christoph Hellwig <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: [e-mail]
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>
---
/* v2 */
unchanged

/* v3 */
unchanged

/* v4 */
- Serge Hallyn <[e-mail]>:
  - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
    terminology consistent.

/* v5 */
unchanged
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837

- Christoph Hellwig <[e-mail]>:
  - Use new file_mnt_user_ns() helper.

/* v6 */
unchanged
base-commit: 19c329f6808995b142b3966301f217c831e7cf31
---
 fs/exec.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Patch

diff --git a/fs/exec.c b/fs/exec.c
index a8ec371cd3cd..d803227805f6 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1404,15 +1404,15 @@  EXPORT_SYMBOL(begin_new_exec);
 void would_dump(struct linux_binprm *bprm, struct file *file)
 {
 	struct inode *inode = file_inode(file);
-	if (inode_permission(&init_user_ns, inode, MAY_READ) < 0) {
+	struct user_namespace *mnt_userns = file_mnt_user_ns(file);
+	if (inode_permission(mnt_userns, inode, MAY_READ) < 0) {
 		struct user_namespace *old, *user_ns;
 		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
 
 		/* Ensure mm->user_ns contains the executable */
 		user_ns = old = bprm->mm->user_ns;
 		while ((user_ns != &init_user_ns) &&
-		       !privileged_wrt_inode_uidgid(user_ns, &init_user_ns,
-						    inode))
+		       !privileged_wrt_inode_uidgid(user_ns, mnt_userns, inode))
 			user_ns = user_ns->parent;
 
 		if (old != user_ns) {