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tty: fix out-of-bounds access in tty_driver_lookup_tty()

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When specifying an invalid console= device like console=tty3270,
tty_driver_lookup_tty() returns the tty struct without checking
whether index is a valid number.

To reproduce:

qemu-system-x86_64 -enable-kvm -nographic -serial mon:stdio \
-kernel ../linux-build-x86/arch/x86/boot/bzImage \
-append "console=ttyS0 console=tty3270"

This crashes with:

[    0.770599] BUG: kernel NULL pointer dereference, address: 00000000000000ef
[    0.771265] #PF: supervisor read access in kernel mode
[    0.771773] #PF: error_code(0x0000) - not-present page
[    0.772609] Oops: 0000 [#1] PREEMPT SMP PTI
[    0.774878] RIP: 0010:tty_open+0x268/0x6f0
[    0.784013]  chrdev_open+0xbd/0x230
[    0.784444]  ? cdev_device_add+0x80/0x80
[    0.784920]  do_dentry_open+0x1e0/0x410
[    0.785389]  path_openat+0xca9/0x1050
[    0.785813]  do_filp_open+0xaa/0x150
[    0.786240]  file_open_name+0x133/0x1b0
[    0.786746]  filp_open+0x27/0x50
[    0.787244]  console_on_rootfs+0x14/0x4d
[    0.787800]  kernel_init_freeable+0x1e4/0x20d
[    0.788383]  ? rest_init+0xc0/0xc0
[    0.788881]  kernel_init+0x11/0x120
[    0.789356]  ret_from_fork+0x22/0x30

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20221209112737.3222509-2-svens@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Schnelle 2022-12-09 12:27:36 +01:00 committed by Greg Kroah-Hartman
parent 9676ab9b07
commit db4df8e9d7
1 changed files with 5 additions and 3 deletions
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8
drivers/tty/tty_io.c
View File

@ -1224,14 +1224,16 @@ static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
{
struct tty_struct *tty;
if (driver->ops->lookup)
if (driver->ops->lookup) {
if (!file)
tty = ERR_PTR(-EIO);
else
tty = driver->ops->lookup(driver, file, idx);
else
} else {
if (idx >= driver->num)
return ERR_PTR(-EINVAL);
tty = driver->ttys[idx];
}
if (!IS_ERR(tty))
tty_kref_get(tty);
return tty;