NULL Pointer Dereference Affecting linux-6.1 package, versions <6.1.119-1~deb11u1


Severity

Recommended
0.0
medium
0
10

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Threat Intelligence

EPSS
0.04% (5th percentile)

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  • Snyk IDSNYK-DEBIAN11-LINUX61-8601437
  • published2 Jan 2025
  • disclosed21 Oct 2024

Introduced: 21 Oct 2024

CVE-2024-50048  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

Upgrade Debian:11 linux-6.1 to version 6.1.119-1~deb11u1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-6.1 package and not the linux-6.1 package as distributed by Debian. See How to fix? for Debian:11 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

syzbot has found a NULL pointer dereference bug in fbcon. Here is the simplified C reproducer:

struct param { uint8_t type; struct tiocl_selection ts; };

int main() { struct fb_con2fbmap con2fb; struct param param;

int fd = open(&#34;/dev/fb1&#34;, 0, 0);

con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &amp;con2fb);

param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0;

int fd1 = open(&#34;/dev/tty1&#34;, O_RDWR, 0); ioctl(fd1, TIOCLINUX, &amp;param);

con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &amp;con2fb);

return 0;

}

After calling ioctl(fd1, TIOCLINUX, &param), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) causes the kernel to follow a different execution path:

set_con2fb_map -> con2fb_init_display -> fbcon_set_disp -> redraw_screen -> hide_cursor -> clear_selection -> highlight -> invert_screen -> do_update_region -> fbcon_putcs -> ops->putcs

Since ops->putcs is a NULL pointer, this leads to a kernel panic. To prevent this, we need to call set_blitting_type() within set_con2fb_map() to properly initialize ops->putcs.

CVSS Scores

version 3.1