| Message ID | 20180116215242.784423-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Hi Arnd, Thank you for the patch. On Tuesday, 16 January 2018 23:52:15 EET Arnd Bergmann wrote: > While experimenting with older compiler versions, I ran > into a warning that no longer shows up on gcc-4.8 or newer: > > drivers/media/platform/s3c-camif/camif-capture.c: In function > '__camif_subdev_try_format': > drivers/media/platform/s3c-camif/camif-capture.c:1265:25: error: array > subscript is below array bounds > > This is an off-by-one bug, leading to an access before the start of the > array, while newer compilers silently assume this undefined behavior > cannot happen and leave the loop at index 0 if no other entry matches. > > As Sylvester explains, we actually need to ensure that the > value is within the range, so this reworks the loop to be > easier to parse correctly, and an additional check to fall > back on the first format value for any unexpected input. > > I found an existing gcc bug for it and added a reduced version > of the function there. > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69249#c3 > Fixes: babde1c243b2 ("[media] V4L: Add driver for S3C24XX/S3C64XX SoC series > camera interface") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > v4: simplify a bit > v3: fix newly introduced off-by-one bug. > v2: rework logic rather than removing it. > --- > drivers/media/platform/s3c-camif/camif-capture.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/media/platform/s3c-camif/camif-capture.c > b/drivers/media/platform/s3c-camif/camif-capture.c index > 437395a61065..9ab8e7ee2e1e 100644 > --- a/drivers/media/platform/s3c-camif/camif-capture.c > +++ b/drivers/media/platform/s3c-camif/camif-capture.c > @@ -1256,16 +1256,17 @@ static void __camif_subdev_try_format(struct > camif_dev *camif, { > const struct s3c_camif_variant *variant = camif->variant; > const struct vp_pix_limits *pix_lim; > - int i = ARRAY_SIZE(camif_mbus_formats); > + unsigned int i; > > /* FIXME: constraints against codec or preview path ? */ > pix_lim = &variant->vp_pix_limits[VP_CODEC]; > > - while (i-- >= 0) > + for (i = 0; i < ARRAY_SIZE(camif_mbus_formats); i++) > if (camif_mbus_formats[i] == mf->code) > break; > > - mf->code = camif_mbus_formats[i]; > + if (i == ARRAY_SIZE(camif_mbus_formats)) > + mf->code = camif_mbus_formats[0]; > > if (pad == CAMIF_SD_PAD_SINK) { > v4l_bound_align_image(&mf->width, 8, CAMIF_MAX_PIX_WIDTH,
On Tue, Jan 16, 2018 at 10:52:15PM +0100, Arnd Bergmann wrote: > While experimenting with older compiler versions, I ran > into a warning that no longer shows up on gcc-4.8 or newer: > > drivers/media/platform/s3c-camif/camif-capture.c: In function '__camif_subdev_try_format': > drivers/media/platform/s3c-camif/camif-capture.c:1265:25: error: array subscript is below array bounds > > This is an off-by-one bug, leading to an access before the start of the > array, while newer compilers silently assume this undefined behavior > cannot happen and leave the loop at index 0 if no other entry matches. > > As Sylvester explains, we actually need to ensure that the > value is within the range, so this reworks the loop to be > easier to parse correctly, and an additional check to fall > back on the first format value for any unexpected input. > > I found an existing gcc bug for it and added a reduced version > of the function there. > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69249#c3 > Fixes: babde1c243b2 ("[media] V4L: Add driver for S3C24XX/S3C64XX SoC series camera interface") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
diff --git a/drivers/media/platform/s3c-camif/camif-capture.c b/drivers/media/platform/s3c-camif/camif-capture.c index 437395a61065..9ab8e7ee2e1e 100644 --- a/drivers/media/platform/s3c-camif/camif-capture.c +++ b/drivers/media/platform/s3c-camif/camif-capture.c @@ -1256,16 +1256,17 @@ static void __camif_subdev_try_format(struct camif_dev *camif, { const struct s3c_camif_variant *variant = camif->variant; const struct vp_pix_limits *pix_lim; - int i = ARRAY_SIZE(camif_mbus_formats); + unsigned int i; /* FIXME: constraints against codec or preview path ? */ pix_lim = &variant->vp_pix_limits[VP_CODEC]; - while (i-- >= 0) + for (i = 0; i < ARRAY_SIZE(camif_mbus_formats); i++) if (camif_mbus_formats[i] == mf->code) break; - mf->code = camif_mbus_formats[i]; + if (i == ARRAY_SIZE(camif_mbus_formats)) + mf->code = camif_mbus_formats[0]; if (pad == CAMIF_SD_PAD_SINK) { v4l_bound_align_image(&mf->width, 8, CAMIF_MAX_PIX_WIDTH,
While experimenting with older compiler versions, I ran into a warning that no longer shows up on gcc-4.8 or newer: drivers/media/platform/s3c-camif/camif-capture.c: In function '__camif_subdev_try_format': drivers/media/platform/s3c-camif/camif-capture.c:1265:25: error: array subscript is below array bounds This is an off-by-one bug, leading to an access before the start of the array, while newer compilers silently assume this undefined behavior cannot happen and leave the loop at index 0 if no other entry matches. As Sylvester explains, we actually need to ensure that the value is within the range, so this reworks the loop to be easier to parse correctly, and an additional check to fall back on the first format value for any unexpected input. I found an existing gcc bug for it and added a reduced version of the function there. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69249#c3 Fixes: babde1c243b2 ("[media] V4L: Add driver for S3C24XX/S3C64XX SoC series camera interface") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- v4: simplify a bit v3: fix newly introduced off-by-one bug. v2: rework logic rather than removing it. --- drivers/media/platform/s3c-camif/camif-capture.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)