[lvc-project] Patch "tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf()" has been added to the 5.10-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf()

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tty-n_gsm-add-sanity-check-for-gsm-receive-in-gsm_receive_buf.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From Ilia.Gavrilov at infotecs.ru Tue Dec 12 12:17:23 2023
From: Gavrilov Ilia <Ilia.Gavrilov at infotecs.ru>
Date: Tue, 12 Dec 2023 11:17:21 +0000
Subject: tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf()
To: "stable at vger.kernel.org" <stable at vger.kernel.org>, Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Daniel Starke <daniel.starke at siemens.com>, Jiri Slaby <jirislaby at kernel.org>, Russ Gorby <russ.gorby at intel.com>, "linux-kernel at vger.kernel.org" <linux-kernel at vger.kernel.org>, "lvc-project at linuxtesting.org" <lvc-project at linuxtesting.org>, "syzbot+e3563f0c94e188366dbb at syzkaller.appspotmail.com" <syzbot+e3563f0c94e188366dbb at syzkaller.appspotmail.com>, Mazin Al Haddad <mazinalhaddad05 at gmail.com>
Message-ID: <20231212111431.4064760-4-Ilia.Gavrilov at infotecs.ru>

From: Mazin Al Haddad <mazinalhaddad05 at gmail.com>

commit f16c6d2e58a4c2b972efcf9eb12390ee0ba3befb upstream

A null pointer dereference can happen when attempting to access the
"gsm->receive()" function in gsmld_receive_buf(). Currently, the code
assumes that gsm->receive is only called after MUX activation.
Since the gsmld_receive_buf() function can be accessed without the need to
initialize the MUX, the gsm->receive() function will not be set and a
NULL pointer dereference will occur.

Fix this by avoiding the call to "gsm->receive()" in case the function is
not initialized by adding a sanity check.

Call Trace:
 <TASK>
 gsmld_receive_buf+0x1c2/0x2f0 drivers/tty/n_gsm.c:2861
 tiocsti drivers/tty/tty_io.c:2293 [inline]
 tty_ioctl+0xa75/0x15d0 drivers/tty/tty_io.c:2692
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Link: https://syzkaller.appspot.com/bug?id=bdf035c61447f8c6e0e6920315d577cb5cc35ac5
Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open")
Reported-and-tested-by: syzbot+e3563f0c94e188366dbb at syzkaller.appspotmail.com
Signed-off-by: Mazin Al Haddad <mazinalhaddad05 at gmail.com>
Link: https://lore.kernel.org/r/20220814015211.84180-1-mazinalhaddad05@gmail.com
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov at infotecs.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/tty/n_gsm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2588,7 +2588,8 @@ static void gsmld_receive_buf(struct tty
 			flags = *fp++;
 		switch (flags) {
 		case TTY_NORMAL:
-			gsm->receive(gsm, *cp);
+			if (gsm->receive)
+				gsm->receive(gsm, *cp);
 			break;
 		case TTY_OVERRUN:
 		case TTY_BREAK:


Patches currently in stable-queue which might be from Ilia.Gavrilov at infotecs.ru are

queue-5.10/tty-n_gsm-add-sanity-check-for-gsm-receive-in-gsm_receive_buf.patch
queue-5.10/tty-n_gsm-fix-tty-registration-before-control-channel-open.patch
queue-5.10/tty-n_gsm-remove-duplicates-of-parameters.patch