5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: George Kennedy <george.kennedy@xxxxxxxxxx>
commit 6eabce6608d6f3440f4c03aa3d3ef50a47a3d193 upstream.
Calling ioctl TIOCSSERIAL with an invalid baud_base can
result in uartclk being zero, which will result in a
divide by zero error in uart_get_divisor(). The check for
uartclk being zero in uart_set_info() needs to be done
before other settings are made as subsequent calls to
ioctl TIOCSSERIAL for the same port would be impacted if
the uartclk check was done where uartclk gets set.
Oops: divide error: 0000 PREEMPT SMP KASAN PTI
RIP: 0010:uart_get_divisor (drivers/tty/serial/serial_core.c:580)
Call Trace:
<TASK>
serial8250_get_divisor (drivers/tty/serial/8250/8250_port.c:2576
drivers/tty/serial/8250/8250_port.c:2589)
serial8250_do_set_termios (drivers/tty/serial/8250/8250_port.c:502
drivers/tty/serial/8250/8250_port.c:2741)
serial8250_set_termios (drivers/tty/serial/8250/8250_port.c:2862)
uart_change_line_settings (./include/linux/spinlock.h:376
./include/linux/serial_core.h:608 drivers/tty/serial/serial_core.c:222)
uart_port_startup (drivers/tty/serial/serial_core.c:342)
uart_startup (drivers/tty/serial/serial_core.c:368)
uart_set_info (drivers/tty/serial/serial_core.c:1034)
uart_set_info_user (drivers/tty/serial/serial_core.c:1059)
tty_set_serial (drivers/tty/tty_io.c:2637)
tty_ioctl (drivers/tty/tty_io.c:2647 drivers/tty/tty_io.c:2791)
__x64_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:907
fs/ioctl.c:893 fs/ioctl.c:893)
do_syscall_64 (arch/x86/entry/common.c:52
(discriminator 1) arch/x86/entry/common.c:83 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx>
Rule: add
Link: https://lore.kernel.org/stable/1721148848-9784-1-git-send-email-george.kennedy%40oracle.com
Link: https://lore.kernel.org/r/1721219078-3209-1-git-send-email-george.kennedy@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -854,6 +854,14 @@ static int uart_set_info(struct tty_stru
new_flags = (__force upf_t)new_info->flags;
old_custom_divisor = uport->custom_divisor;
+ if (!(uport->flags & UPF_FIXED_PORT)) {
+ unsigned int uartclk = new_info->baud_base * 16;
+ /* check needs to be done here before other settings made */
+ if (uartclk == 0) {
+ retval = -EINVAL;
+ goto exit;
+ }
+ }
if (!capable(CAP_SYS_ADMIN)) {
retval = -EPERM;
if (change_irq || change_port ||
