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Subject[ 39/42] cred: copy_process() should clear child->replacement_session_keyring
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Oleg Nesterov <oleg@redhat.com>

commit 79549c6dfda0603dba9a70a53467ce62d9335c33 upstream.

keyctl_session_to_parent(task) sets ->replacement_session_keyring,
it should be processed and cleared by key_replace_session_keyring().

However, this task can fork before it notices TIF_NOTIFY_RESUME and
the new child gets the bogus ->replacement_session_keyring copied by
dup_task_struct(). This is obviously wrong and, if nothing else, this
leads to put_cred(already_freed_cred).

change copy_creds() to clear this member. If copy_process() fails
before this point the wrong ->replacement_session_keyring doesn't
matter, exit_creds() won't be called.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/cred.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -385,6 +385,8 @@ int copy_creds(struct task_struct *p, un
struct cred *new;
int ret;

+ p->replacement_session_keyring = NULL;
+
if (
#ifdef CONFIG_KEYS
!p->cred->thread_keyring &&



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