| Message ID | 20170912200932.3634089-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/12/2017 10:09 PM, 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. > > Since the code is not only wrong, but also has no effect besides the > out-of-bounds access, this patch just removes it. > > 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> > --- > drivers/media/platform/s3c-camif/camif-capture.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/drivers/media/platform/s3c-camif/camif-capture.c b/drivers/media/platform/s3c-camif/camif-capture.c > index 25c7a7d42292..c6921f6a5a6a 100644 > --- a/drivers/media/platform/s3c-camif/camif-capture.c > +++ b/drivers/media/platform/s3c-camif/camif-capture.c > @@ -1256,17 +1256,10 @@ 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); > > /* FIXME: constraints against codec or preview path ? */ > pix_lim = &variant->vp_pix_limits[VP_CODEC]; > > - while (i-- >= 0) > - if (camif_mbus_formats[i] == mf->code) > - break; > - > - mf->code = camif_mbus_formats[i]; Interesting finding... the function needs to ensure mf->code is set to one of supported values by the driver, so instead of removing how about changing the above line to: if (i < 0) mf->code = camif_mbus_formats[0]; ?
On Wed, Sep 13, 2017 at 11:25 AM, Sylwester Nawrocki <s.nawrocki@samsung.com> wrote: > On 09/12/2017 10:09 PM, Arnd Bergmann wrote: >> { >> const struct s3c_camif_variant *variant = camif->variant; >> const struct vp_pix_limits *pix_lim; >> - int i = ARRAY_SIZE(camif_mbus_formats); >> >> /* FIXME: constraints against codec or preview path ? */ >> pix_lim = &variant->vp_pix_limits[VP_CODEC]; >> >> - while (i-- >= 0) >> - if (camif_mbus_formats[i] == mf->code) >> - break; >> - >> - mf->code = camif_mbus_formats[i]; > > > Interesting finding... the function needs to ensure mf->code is set > to one of supported values by the driver, so instead of removing > how about changing the above line to: > > if (i < 0) > mf->code = camif_mbus_formats[0]; > > ? That would still have one of the two out-of-bounds accesses ;-) maybe this for (i = 0; i < ARRAY_SIZE(camif_mbus_formats); i++) if (camif_mbus_formats[i] == mf->code) break; if (i == ARRAY_SIZE(camif_mbus_formats)) mf->code = camif_mbus_formats[0]; Arnd
On 09/13/2017 04:03 PM, Arnd Bergmann wrote: > On Wed, Sep 13, 2017 at 11:25 AM, Sylwester Nawrocki > <s.nawrocki@samsung.com> wrote: >> On 09/12/2017 10:09 PM, Arnd Bergmann wrote: >>> { >>> const struct s3c_camif_variant *variant = camif->variant; >>> const struct vp_pix_limits *pix_lim; >>> - int i = ARRAY_SIZE(camif_mbus_formats); >>> >>> /* FIXME: constraints against codec or preview path ? */ >>> pix_lim = &variant->vp_pix_limits[VP_CODEC]; >>> >>> - while (i-- >= 0) >>> - if (camif_mbus_formats[i] == mf->code) >>> - break; >>> - >>> - mf->code = camif_mbus_formats[i]; >> >> Interesting finding... the function needs to ensure mf->code is set >> to one of supported values by the driver, so instead of removing >> how about changing the above line to: >> >> if (i < 0) >> mf->code = camif_mbus_formats[0]; >> >> ? > That would still have one of the two out-of-bounds accesses;-) Ah, indeed :/ > maybe this > > for (i = 0; i < ARRAY_SIZE(camif_mbus_formats); i++) > if (camif_mbus_formats[i] == mf->code) > break; > > if (i == ARRAY_SIZE(camif_mbus_formats)) > mf->code = camif_mbus_formats[0]; Yes, it should work that way.
diff --git a/drivers/media/platform/s3c-camif/camif-capture.c b/drivers/media/platform/s3c-camif/camif-capture.c index 25c7a7d42292..c6921f6a5a6a 100644 --- a/drivers/media/platform/s3c-camif/camif-capture.c +++ b/drivers/media/platform/s3c-camif/camif-capture.c @@ -1256,17 +1256,10 @@ 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); /* FIXME: constraints against codec or preview path ? */ pix_lim = &variant->vp_pix_limits[VP_CODEC]; - while (i-- >= 0) - if (camif_mbus_formats[i] == mf->code) - break; - - mf->code = camif_mbus_formats[i]; - if (pad == CAMIF_SD_PAD_SINK) { v4l_bound_align_image(&mf->width, 8, CAMIF_MAX_PIX_WIDTH, ffs(pix_lim->out_width_align) - 1,
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. Since the code is not only wrong, but also has no effect besides the out-of-bounds access, this patch just removes it. 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> --- drivers/media/platform/s3c-camif/camif-capture.c | 7 ------- 1 file changed, 7 deletions(-)