Hi Tuo, Helge,

On Wed, 10 Jun 2026 at 04:50, Tuo Li [off-list ref] wrote:

If mode_option is NULL, it is assigned from mode_option_buf:

  if (!mode_option) {
    fb_get_options(NULL, &mode_option_buf);
    mode_option = mode_option_buf;
  }

Later, name is assigned from mode_option:

  const char *name = mode_option;

However, mode_option_buf is freed before name is no longer used:

  kfree(mode_option_buf);

while name is still accessed by:

  if ((name_matches(db[i], name, namelen) ||

Since name aliases mode_option_buf, this may result in a
use-after-free.

Fix this by extending the lifetime of mode_option_buf until the end of the
function and using scope-based resource management for cleanup.

Signed-off-by: Tuo Li <redacted>
---
v2:
* Use scope-based resource management instead of manual kfree() calls.
  Thanks to Helge Deller for the helpful advice.

Thanks for your patch, which is now commit 85b6256469cebdac ("fbdev:
modedb: fix a possible UAF in fb_find_mode()") in fbdev/for-next, and has:

    Cc: stable@vger.kernel.org # v6.5+

I believe it needs:
Fixes: 089d924d03d5c17b ("fbdev: Read video= option with
fb_get_option() in modedb")

and that commit entered v6.4-rc1, i.e. not v6.5?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds