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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>
master
Christian Brauner 2021-01-21 14:19:41 +01:00
parent 0f5d220b42
commit 435ac6214e
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 3 additions and 3 deletions
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6
fs/exec.c
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@ -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) {