From: Mazin Al Haddad <mazinalhaddad05@gmail.com> To: gregkh@linuxfoundation.org Cc: jirislaby@kernel.org, daniel.starke@siemens.com, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, skhan@linuxfoundation.org, paskripkin@gmail.com, Mazin Al Haddad <mazinalhaddad05@gmail.com>, syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Subject: [PATCH v2] tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf() Date: Sun, 14 Aug 2022 04:52:12 +0300 [thread overview] Message-ID: <20220814015211.84180-1-mazinalhaddad05@gmail.com> (raw) A null pointer dereference can happen when attempting to access the "gsm->receive()" function in gsmld_receive_buf(). Currently, the code assumes that gsm->recieve 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 Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open") Link: https://syzkaller.appspot.com/bug?id=bdf035c61447f8c6e0e6920315d577cb5cc35ac5 Reported-and-tested-by: syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Signed-off-by: Mazin Al Haddad <mazinalhaddad05@gmail.com> --- v1->v2: - Change commit title and description, removing unneeded and unclear references to syzbot bug. - Use a sanity check instead of reinitializing gsm->receive in gsmld_attach_gsm() drivers/tty/n_gsm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index caa5c14ed57f..38688cb16c20 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2858,7 +2858,8 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp, 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: -- 2.37.2
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From: Mazin Al Haddad <mazinalhaddad05@gmail.com> To: gregkh@linuxfoundation.org Cc: daniel.starke@siemens.com, jirislaby@kernel.org, paskripkin@gmail.com, syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Mazin Al Haddad <mazinalhaddad05@gmail.com> Subject: [PATCH v2] tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf() Date: Sun, 14 Aug 2022 04:52:12 +0300 [thread overview] Message-ID: <20220814015211.84180-1-mazinalhaddad05@gmail.com> (raw) A null pointer dereference can happen when attempting to access the "gsm->receive()" function in gsmld_receive_buf(). Currently, the code assumes that gsm->recieve 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 Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open") Link: https://syzkaller.appspot.com/bug?id=bdf035c61447f8c6e0e6920315d577cb5cc35ac5 Reported-and-tested-by: syzbot+e3563f0c94e188366dbb@syzkaller.appspotmail.com Signed-off-by: Mazin Al Haddad <mazinalhaddad05@gmail.com> --- v1->v2: - Change commit title and description, removing unneeded and unclear references to syzbot bug. - Use a sanity check instead of reinitializing gsm->receive in gsmld_attach_gsm() drivers/tty/n_gsm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index caa5c14ed57f..38688cb16c20 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2858,7 +2858,8 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp, 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: -- 2.37.2 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
next reply other threads:[~2022-08-14 1:55 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-08-14 1:52 Mazin Al Haddad [this message] 2022-08-14 1:52 ` [PATCH v2] tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf() Mazin Al Haddad
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