linux-kernel - [ 054/180] cred: copy_process() should clear child->replacement_session

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Message-Id: <20121001225159.902084886@1wt.eu>
Date:	Tue, 02 Oct 2012 00:52:51 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Oleg Nesterov <oleg@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Willy Tarreau <w@....eu>
Subject: [ 054/180] cred: copy_process() should clear child->replacement_session_keyring

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@...hat.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.

Cc: <stable@...r.kernel.org>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: David Howells <dhowells@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/cred.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index 0b5b5fc..9c06d10 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -443,6 +443,8 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)

 	mutex_init(&p->cred_guard_mutex);

+	p->replacement_session_keyring = NULL;
+
 	if (
 #ifdef CONFIG_KEYS
 		!p->cred->thread_keyring &&
-- 
1.7.2.1.45.g54fbc

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