[PATCH v3 27/38] would_dump: handle idmapped mounts

Christian Brauner
2020-11-28T22:14:39Z

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.

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
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged

/* v3 */
unchanged
---
fs/exec.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index b499a1a03934..10c06fdf78a7 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1391,14 +1391,15 @@ 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 *ns = mnt_user_ns(file->f_path.mnt);
+ if (inode_permission(ns, 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, ns, inode))
user_ns = user_ns->parent;

if (old != user_ns) {
--
2.29.2