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SubjectRe: [PATCH] drm/modes: Fix unterminated strncpy
On Tue, Jul 30, 2019 at 04:40:32PM +0800, Chuhong Yuan wrote:
> strncpy(dest, src, strlen(src)) leads to unterminated
> dest, which is dangerous.
> Fix it by using strscpy.
>
> Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
> ---
> drivers/gpu/drm/drm_modes.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index 80fcd5dc1558..170fc24e0f31 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -1770,7 +1770,7 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
> }
>
> if (named_mode) {
> - strncpy(mode->name, name, mode_end);
> + strscpy(mode->name, name, mode_end + 1);

Shouldn't you be checking that mode_end + 1 is not > than the size of mode->name
(ie: DRM_DISPLAY_MODE_LEN)? This still seems unsafe.

Sean

> } else {
> ret = drm_mode_parse_cmdline_res_mode(name, mode_end,
> parse_extras,
> --
> 2.20.1
>

--
Sean Paul, Software Engineer, Google / Chromium OS

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