Unverified Commit 435ac621 authored Jan 21, 2021 by Christian Brauner

would_dump: handle idmapped mounts

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/20210121131959.646623-23-christian.brauner@ubuntu.com


Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

parent 0f5d220b

fs/exec.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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) {