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authorOleg Nesterov <oleg@redhat.com>2012-05-11 04:59:08 +0400
committerAl Viro <viro@zeniv.linux.org.uk>2012-05-24 06:11:23 +0400
commit413cd3d9abeaef590e5ce00564f7a443165db238 (patch)
treefc7d254053793a95d1470f7c9eafb782d8cf91d6 /security/keys/process_keys.c
parent4d1d61a6b203d957777d73fcebf19d90b038b5b2 (diff)
downloadlinux-413cd3d9abeaef590e5ce00564f7a443165db238.tar.xz
keys: change keyctl_session_to_parent() to use task_work_add()
Change keyctl_session_to_parent() to use task_work_add() and move key_replace_session_keyring() logic into task_work->func(). Note that we do task_work_cancel() before task_work_add() to ensure that only one work can be pending at any time. This is important, we must not allow user-space to abuse the parent's ->task_works list. The callback, replace_session_keyring(), checks PF_EXITING. I guess this is not really needed but looks better. As a side effect, this fixes the (unlikely) race. The callers of key_replace_session_keyring() and keyctl_session_to_parent() lack the necessary barriers, the parent can miss the request. Now we can remove task_struct->replacement_session_keyring and related code. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexander Gordeev <agordeev@redhat.com> Cc: Chris Zankel <chris@zankel.net> Cc: David Smith <dsmith@redhat.com> Cc: "Frank Ch. Eigler" <fche@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'security/keys/process_keys.c')
-rw-r--r--security/keys/process_keys.c20
1 files changed, 7 insertions, 13 deletions
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index d71056db7b67..4ad54eea1ea4 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -834,23 +834,17 @@ error:
* Replace a process's session keyring on behalf of one of its children when
* the target process is about to resume userspace execution.
*/
-void key_replace_session_keyring(void)
+void key_change_session_keyring(struct task_work *twork)
{
- const struct cred *old;
- struct cred *new;
-
- if (!current->replacement_session_keyring)
- return;
+ const struct cred *old = current_cred();
+ struct cred *new = twork->data;
- write_lock_irq(&tasklist_lock);
- new = current->replacement_session_keyring;
- current->replacement_session_keyring = NULL;
- write_unlock_irq(&tasklist_lock);
-
- if (!new)
+ kfree(twork);
+ if (unlikely(current->flags & PF_EXITING)) {
+ put_cred(new);
return;
+ }
- old = current_cred();
new-> uid = old-> uid;
new-> euid = old-> euid;
new-> suid = old-> suid;