From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9008225DB11; Tue, 25 Mar 2025 12:39:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906376; cv=none; b=LpO6bvRMkDJj/JtRVJAy0IB6SCICTvxtCxIVJmWSeM8vRlNahBsElEBffLcf2Np3zP7d0FTY96E8Kh9/BrQreYVStItRZwhJNNQz5Wqw4cliwezYFYhVh65VmVSRoYHHgz/o4mWP+2+p+YL5GiB5MO3UkNx7yikOm+luEqaJx0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906376; c=relaxed/simple; bh=dN4cHZgQGkT7qf/1VxEeLXaLWJHpmOQDmJ6zJQq/or0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZPgs5tMuRFKnHwt6kMbdowXghgwIJaTBtRUPbD/Mb7rDN1lJVS8tJqgN3py8g1W+93hq2A+a3zWbc63RE5SQ3XvK1WIcf4bdRXEAkKsoe+niRorChUeaRB5aEjcTEXlie9r3TlMXrbgX/9T1pfWjBU6H+NRNZuh0zFaqxZcOXlg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LqhOpzh9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LqhOpzh9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40630C4CEE4; Tue, 25 Mar 2025 12:39:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742906376; bh=dN4cHZgQGkT7qf/1VxEeLXaLWJHpmOQDmJ6zJQq/or0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LqhOpzh9TWjvMti6GpU/31+eXcDQRnVhhG8nPrUSXsNI7+Ms8WUcEvOmVXrVfVGRt OEuYPG4EhIaYFMMbkn6muaegqrW4R037aCSxACPgpxmeaZha3qkqNC39qE/RGvmm7R qGR4kXXwgK1p/hHsVsgk54sL3EAqhyLixpudAzCY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+6105ffc1ded71d194d6d@syzkaller.appspotmail.com, David Howells , Oleg Nesterov , Jarkko Sakkinen Subject: [PATCH 6.12 084/116] keys: Fix UAF in key_put() Date: Tue, 25 Mar 2025 08:22:51 -0400 Message-ID: <20250325122151.359494355@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250325122149.207086105@linuxfoundation.org> References: <20250325122149.207086105@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Howells commit 75845c6c1a64483e9985302793dbf0dfa5f71e32 upstream. Once a key's reference count has been reduced to 0, the garbage collector thread may destroy it at any time and so key_put() is not allowed to touch the key after that point. The most key_put() is normally allowed to do is to touch key_gc_work as that's a static global variable. However, in an effort to speed up the reclamation of quota, this is now done in key_put() once the key's usage is reduced to 0 - but now the code is looking at the key after the deadline, which is forbidden. Fix this by using a flag to indicate that a key can be gc'd now rather than looking at the key's refcount in the garbage collector. Fixes: 9578e327b2b4 ("keys: update key quotas in key_put()") Reported-by: syzbot+6105ffc1ded71d194d6d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/673b6aec.050a0220.87769.004a.GAE@google.com/ Signed-off-by: David Howells Tested-by: syzbot+6105ffc1ded71d194d6d@syzkaller.appspotmail.com Reviewed-by: Oleg Nesterov Signed-off-by: Jarkko Sakkinen Signed-off-by: Greg Kroah-Hartman --- include/linux/key.h | 1 + security/keys/gc.c | 4 +++- security/keys/key.c | 2 ++ 3 files changed, 6 insertions(+), 1 deletion(-) --- a/include/linux/key.h +++ b/include/linux/key.h @@ -236,6 +236,7 @@ struct key { #define KEY_FLAG_ROOT_CAN_INVAL 7 /* set if key can be invalidated by root without permission */ #define KEY_FLAG_KEEP 8 /* set if key should not be removed */ #define KEY_FLAG_UID_KEYRING 9 /* set if key is a user or user session keyring */ +#define KEY_FLAG_FINAL_PUT 10 /* set if final put has happened on key */ /* the key type and key description string * - the desc is used to match a key against search criteria --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -218,8 +218,10 @@ continue_scanning: key = rb_entry(cursor, struct key, serial_node); cursor = rb_next(cursor); - if (refcount_read(&key->usage) == 0) + if (test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) { + smp_mb(); /* Clobber key->user after FINAL_PUT seen. */ goto found_unreferenced_key; + } if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) { if (key->type == key_gc_dead_keytype) { --- a/security/keys/key.c +++ b/security/keys/key.c @@ -658,6 +658,8 @@ void key_put(struct key *key) key->user->qnbytes -= key->quotalen; spin_unlock_irqrestore(&key->user->lock, flags); } + smp_mb(); /* key->user before FINAL_PUT set. */ + set_bit(KEY_FLAG_FINAL_PUT, &key->flags); schedule_work(&key_gc_work); } }