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From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To: unlisted-recipients:; (no To-header on input)
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-media@vger.kernel.org, devel@driverdev.osuosl.org,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Subject: [PATCH v2 25/41] media: atomisp: Avoid overflow in compute_blending
Date: Sat, 30 May 2020 08:55:42 +0200
Message-ID: <22b531f57658727abacb28f534d6fc9d44eee4cf.1590821410.git.mchehab+huawei@kernel.org> (raw)
In-Reply-To: <cover.1590821410.git.mchehab+huawei@kernel.org>

From: Nathan Chancellor <natechancellor@gmail.com>

Clang warns:

drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c:129:35:
warning: implicit conversion from 'unsigned long' to 'int32_t' (aka
'int') changes value from 18446744073709543424 to -8192
[-Wconstant-conversion]
        return MAX(MIN(isp_strength, 0), -XNR_BLENDING_SCALE_FACTOR);
        ~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

XNR_BLENDING_SCALE_FACTOR is BIT(13), or 8192, which will easily fit
into a signed 32-bit integer. However, it is an unsigned long, which
means that negating it is the same as subtracting that value from
ULONG_MAX + 1, which causes it to be larger than a signed 32-bit
integer so it gets implicitly converted.

We can avoid this by using the variable isp_scale, which holds the value
of XNR_BLENDING_SCALE_FACTOR already, where the implicit conversion from
unsigned long to s32 already happened. If that were to ever overflow,
clang would warn: https://godbolt.org/z/EeSxLG

Link: https://github.com/ClangBuiltLinux/linux/issues/1036

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 .../atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c b/drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c
index a9db6366d20b..629f07faf20a 100644
--- a/drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c
+++ b/drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c
@@ -126,7 +126,7 @@ compute_blending(int strength)
 	 * exactly as s0.11 fixed point, but -1.0 can.
 	 */
 	isp_strength = -(((strength * isp_scale) + offset) / host_scale);
-	return MAX(MIN(isp_strength, 0), -XNR_BLENDING_SCALE_FACTOR);
+	return MAX(MIN(isp_strength, 0), -isp_scale);
 }
 
 void
-- 
2.26.2


  parent reply	other threads:[~2020-05-30  6:58 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-30  6:55 [PATCH v2 00/41] More atomisp fixes and cleanups Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 01/41] media: atomisp: simplify hive_isp_css_mm_hrt wrapper Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 02/41] media: atomisp: get rid of the hrt/hive_isp_css_mm_hrt abstraction layer Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 03/41] media: atomisp: reduce abstraction at ia_css_memory_access Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 04/41] media: atomisp: go one step further to drop ia_css_memory_access.c Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 05/41] media: atomisp: get rid of mmgr_load and mmgr_store Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 06/41] media: atomisp: get rid of unused memory_realloc code Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 07/41] media: atomisp: change the type returned by mmgr alloc Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 08/41] media: atomisp: get rid of memory_access.c Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 09/41] media: atomisp: hmm_bo: untag user pointers Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 10/41] media: atomisp: add debug message to help debugging hmm code Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 11/41] media: atomisp: use Yocto Aero default hmm pool sizes Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 12/41] media: atomisp: get rid of a warning message Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 13/41] media: atomisp: fix driver caps Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 14/41] media: atomisp: use pin_user_pages() for memory allocation Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 15/41] media: atomisp: add debug for hmm alloc Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 16/41] media: atomisp: improve warning for IRQ enable function Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 17/41] media: atomisp: add debug functions for received events Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 18/41] media: atomisp: add more comments about frame allocation Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 19/41] media: atomisp: remove kvmalloc/kvcalloc abstractions Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 20/41] media: atomisp: avoid OOPS due to non-existing ref_frames Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 21/41] media: atomisp: Clean up if block in sh_css_sp_init_stage Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 22/41] media: atomisp: Remove second increment of count in atomisp_subdev_probe Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 23/41] media: atomisp: Remove unnecessary NULL checks in ia_css_pipe_load_extension Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 24/41] media: atomisp: Remove unnecessary NULL check in atomisp_param Mauro Carvalho Chehab
2020-05-30  6:55 ` Mauro Carvalho Chehab [this message]
2020-05-30  6:55 ` [PATCH v2 26/41] media: atomisp: Remove binary_supports_input_format Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 27/41] media: atomisp: avoid an extra memset() when alloc memory Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 28/41] media: atomisp: remove some trivial wrappers from compat css20 Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 29/41] media: atomisp: do another round of coding style cleanup Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 31/41] media: atomisp: get rid of an error abstraction layer Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 32/41] media: atomisp: don't cause a warn if probe failed Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 33/41] media: atomisp: get rid of a bunch of other wrappers Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 34/41] media: atomisp: get rid of system_types.h Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 35/41] media: atomisp: provide more details about the firmware binaries Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 36/41] media: atomisp: print firmware data during load Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 37/41] media: atomisp: allow passing firmware name at modprobe time Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 38/41] media: atomisp: add a debug message at hmm free Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 39/41] media: atomisp: add some debug messages when binaries are used Mauro Carvalho Chehab
2020-05-30  6:55 ` [PATCH v2 40/41] media: atomisp: get rid of set_fs() dirty hacks Mauro Carvalho Chehab

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