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 8BEC01D68D for ; Wed, 4 Oct 2023 18:20:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kR4L9ciB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8609FC433C8; Wed, 4 Oct 2023 18:20:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1696443630; bh=+g+/Y8bUhwqWUOAsq4aLIISw9veiwxng81GuE1vYuBM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kR4L9ciBRIGobMhKfDiDO7i2RIk3cUryE9mCSNF2g/lbEXKzuZC7y3FnNFJqHZ6uq 1rdR9mkfm/g/ivTOULcYQNXZSYO0ynX9lt7n2ooG1RZXtDUzszNMIwj9VDHfJgNa0p 7TIEVfyCWCvrTn2OhBNod58Vqbr9pWsFtgF6AVMo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Daniel Starke Subject: [PATCH 6.1 217/259] Revert "tty: n_gsm: fix UAF in gsm_cleanup_mux" Date: Wed, 4 Oct 2023 19:56:30 +0200 Message-ID: <20231004175227.286633566@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231004175217.404851126@linuxfoundation.org> References: <20231004175217.404851126@linuxfoundation.org> User-Agent: quilt/0.67 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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Starke commit 29346e217b8ab8a52889b88f00b268278d6b7668 upstream. This reverts commit 9b9c8195f3f0d74a826077fc1c01b9ee74907239. The commit above is reverted as it did not solve the original issue. gsm_cleanup_mux() tries to free up the virtual ttys by calling gsm_dlci_release() for each available DLCI. There, dlci_put() is called to decrease the reference counter for the DLCI via tty_port_put() which finally calls gsm_dlci_free(). This already clears the pointer which is being checked in gsm_cleanup_mux() before calling gsm_dlci_release(). Therefore, it is not necessary to clear this pointer in gsm_cleanup_mux() as done in the reverted commit. The commit introduces a null pointer dereference: ? __die+0x1f/0x70 ? page_fault_oops+0x156/0x420 ? search_exception_tables+0x37/0x50 ? fixup_exception+0x21/0x310 ? exc_page_fault+0x69/0x150 ? asm_exc_page_fault+0x26/0x30 ? tty_port_put+0x19/0xa0 gsmtty_cleanup+0x29/0x80 [n_gsm] release_one_tty+0x37/0xe0 process_one_work+0x1e6/0x3e0 worker_thread+0x4c/0x3d0 ? __pfx_worker_thread+0x10/0x10 kthread+0xe1/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2f/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 The actual issue is that nothing guards dlci_put() from being called multiple times while the tty driver was triggered but did not yet finished calling gsm_dlci_free(). Fixes: 9b9c8195f3f0 ("tty: n_gsm: fix UAF in gsm_cleanup_mux") Cc: stable Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20230914051507.3240-1-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2509,10 +2509,8 @@ static void gsm_cleanup_mux(struct gsm_m gsm->has_devices = false; } for (i = NUM_DLCI - 1; i >= 0; i--) - if (gsm->dlci[i]) { + if (gsm->dlci[i]) gsm_dlci_release(gsm->dlci[i]); - gsm->dlci[i] = NULL; - } mutex_unlock(&gsm->mutex); /* Now wipe the queues */ tty_ldisc_flush(gsm->tty);