linux-kernel - Coverity: drm_mode_parse_cmdline_named_mode(): Security best practices violations

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Date:   Thu, 17 Nov 2022 14:18:18 -0800
From:   coverity-bot <keescook@...omium.org>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        David Airlie <airlied@...il.com>,
        dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-next@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Coverity: drm_mode_parse_cmdline_named_mode(): Security best
 practices violations

Hello!

This is an experimental semi-automated report about issues detected by
Coverity from a scan of next-20221117 as part of the linux-next scan project:
https://scan.coverity.com/projects/linux-next-weekly-scan

You're getting this email because you were associated with the identified
lines of code (noted below) that were touched by commits:

  Tue Nov 15 10:09:44 2022 +0100
    a7ab155397dd ("drm/modes: Switch to named mode descriptors")

Coverity reported the following:

*** CID 1527354:  Security best practices violations  (STRING_OVERFLOW)
drivers/gpu/drm/drm_modes.c:1812 in drm_mode_parse_cmdline_named_mode()
1806     		int ret;
1807
1808     		ret = str_has_prefix(name, mode->name);
1809     		if (ret != name_end)
1810     			continue;
1811
vvv     CID 1527354:  Security best practices violations  (STRING_OVERFLOW)
vvv     You might overrun the 32-character fixed-size string "cmdline_mode->name" by copying "mode->name" without checking the length.
1812     		strcpy(cmdline_mode->name, mode->name);
1813     		cmdline_mode->pixel_clock = mode->pixel_clock_khz;
1814     		cmdline_mode->xres = mode->xres;
1815     		cmdline_mode->yres = mode->yres;
1816     		cmdline_mode->interlace = !!(mode->flags & DRM_MODE_FLAG_INTERLACE);
1817     		cmdline_mode->specified = true;

If this is a false positive, please let us know so we can mark it as
such, or teach the Coverity rules to be smarter. If not, please make
sure fixes get into linux-next. :) For patches fixing this, please
include these lines (but double-check the "Fixes" first):

Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
Addresses-Coverity-ID: 1527354 ("Security best practices violations")
Fixes: a7ab155397dd ("drm/modes: Switch to named mode descriptors")

Since mode->name is unbounded, this may overrun cmdline_mode->name
without CONFIG_FORTIFY_SOURCE=y. Please use strscpy().

Thanks for your attention!

-- 
Coverity-bot