tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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User namespaces: Only put the userns when we unhash the uid

uids in namespaces other than init don't get a sysfs entry.

For those in the init namespace, while we're waiting to remove
the sysfs entry for the uid the uid is still hashed, and
alloc_uid() may re-grab that uid without getting a new
reference to the user_ns, which we've already put in free_user
before scheduling remove_user_sysfs_dir().

Reported-and-tested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Tested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

authored by

Serge E. Hallyn and committed by
Linus Torvalds fb5ae64f 37bed900

+1 -2
+1 -2
kernel/user.c
··· 72 72 static void uid_hash_remove(struct user_struct *up) 73 73 { 74 74 hlist_del_init(&up->uidhash_node); 75 + put_user_ns(up->user_ns); 75 76 } 76 77 77 78 static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent) ··· 335 334 atomic_inc(&up->__count); 336 335 spin_unlock_irqrestore(&uidhash_lock, flags); 337 336 338 - put_user_ns(up->user_ns); 339 337 INIT_WORK(&up->work, remove_user_sysfs_dir); 340 338 schedule_work(&up->work); 341 339 } ··· 357 357 sched_destroy_user(up); 358 358 key_put(up->uid_keyring); 359 359 key_put(up->session_keyring); 360 - put_user_ns(up->user_ns); 361 360 kmem_cache_free(uid_cachep, up); 362 361 } 363 362