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drm/displayid: add displayid_get_header() and check bounds better

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[ Upstream commit 5bacecc3c56131c31f18b23d366f2184328fd9cf ]

Add a helper to get a pointer to struct displayid_header. To be
pedantic, add buffer overflow checks to not touch the base if that
itself would overflow.

Cc: Iaroslav Boliukin <iam@lach.pw>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/4a03b3a5132642d3cdb6d4c2641422955a917292.1676580180.git.jani.nikula@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jani Nikula 2023-02-16 22:44:58 +02:00 committed by Greg Kroah-Hartman
parent 48960a503f
commit 4b17053ba2
1 changed files with 16 additions and 1 deletions
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17
drivers/gpu/drm/drm_displayid.c
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@ -7,13 +7,28 @@
#include <drm/drm_edid.h>
#include <drm/drm_print.h>
static const struct displayid_header *
displayid_get_header(const u8 *displayid, int length, int index)
{
const struct displayid_header *base;
if (sizeof(*base) > length - index)
return ERR_PTR(-EINVAL);
base = (const struct displayid_header *)&displayid[index];
return base;
}
static int validate_displayid(const u8 *displayid, int length, int idx)
{
int i, dispid_length;
u8 csum = 0;
const struct displayid_header *base;
base = (const struct displayid_header *)&displayid[idx];
base = displayid_get_header(displayid, length, idx);
if (IS_ERR(base))
return PTR_ERR(base);
DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
base->rev, base->bytes, base->prod_id, base->ext_count);