From: Harry Wentland <harry.wentland@amd.com> To: "Michel Dänzer" <michel@daenzer.net>, "Gustavo A. R. Silva" <gustavo@embeddedor.com>, "Alex Deucher" <alexander.deucher@amd.com>, "Christian König" <christian.koenig@amd.com>, "David (ChunMing) Zhou" <David1.Zhou@amd.com>, "David Airlie" <airlied@linux.ie> Cc: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/amd/display/dc/dce: Fix multiple potential integer overflows Date: Wed, 4 Jul 2018 13:51:08 -0400 [thread overview] Message-ID: <421747e5-e6e0-6680-e3b7-a3a2a5b7b307@amd.com> (raw) In-Reply-To: <c663121e-1db8-9d7f-6b66-2c41e6a8bb70@daenzer.net> On 2018-07-04 03:38 AM, Michel Dänzer wrote: > On 2018-07-04 03:13 AM, Gustavo A. R. Silva wrote: >> Add suffix ULL to constant 5 and cast variables target_pix_clk_khz and >> feedback_divider to uint64_t in order to avoid multiple potential integer >> overflows and give the compiler complete information about the proper >> arithmetic to use. >> >> Notice that such constant and variables are used in contexts that >> expect expressions of type uint64_t (64 bits, unsigned). The current >> casts to uint64_t effectively apply to each expression as a whole, >> but they do not prevent them from being evaluated using 32-bit >> arithmetic instead of 64-bit arithmetic. >> >> Also, once the expressions are properly evaluated using 64-bit >> arithmentic, there is no need for the parentheses that enclose >> them. >> >> Addresses-Coverity-ID: 1460245 ("Unintentional integer overflow") >> Addresses-Coverity-ID: 1460286 ("Unintentional integer overflow") >> Addresses-Coverity-ID: 1460401 ("Unintentional integer overflow") >> Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> >> [...] >> >> @@ -145,8 +145,8 @@ static bool calculate_fb_and_fractional_fb_divider( >> * of fractional feedback decimal point and the fractional FB Divider precision >> * is 2 then the equation becomes (ullfeedbackDivider + 5*100) / (10*100))*/ >> >> - feedback_divider += (uint64_t) >> - (5 * calc_pll_cs->fract_fb_divider_precision_factor); >> + feedback_divider += 5UL * >> + calc_pll_cs->fract_fb_divider_precision_factor; > > This should be 5ULL, as the commit log says, otherwise it's still only > 32 bits on 32-bit platforms. > Agreed. Otherwise this looks good. With that fixed this patch is Reviewed-by: Harry Wentland <harry.wentland@amd.com> Harry >
WARNING: multiple messages have this Message-ID (diff)
From: Harry Wentland <harry.wentland-5C7GfCeVMHo@public.gmane.org> To: "Michel Dänzer" <michel-otUistvHUpPR7s880joybQ@public.gmane.org>, "Gustavo A. R. Silva" <gustavo-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org>, "Alex Deucher" <alexander.deucher-5C7GfCeVMHo@public.gmane.org>, "Christian König" <christian.koenig-5C7GfCeVMHo@public.gmane.org>, "David (ChunMing) Zhou" <David1.Zhou-5C7GfCeVMHo@public.gmane.org>, "David Airlie" <airlied-cv59FeDIM0c@public.gmane.org> Cc: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [PATCH] drm/amd/display/dc/dce: Fix multiple potential integer overflows Date: Wed, 4 Jul 2018 13:51:08 -0400 [thread overview] Message-ID: <421747e5-e6e0-6680-e3b7-a3a2a5b7b307@amd.com> (raw) In-Reply-To: <c663121e-1db8-9d7f-6b66-2c41e6a8bb70-otUistvHUpPR7s880joybQ@public.gmane.org> On 2018-07-04 03:38 AM, Michel Dänzer wrote: > On 2018-07-04 03:13 AM, Gustavo A. R. Silva wrote: >> Add suffix ULL to constant 5 and cast variables target_pix_clk_khz and >> feedback_divider to uint64_t in order to avoid multiple potential integer >> overflows and give the compiler complete information about the proper >> arithmetic to use. >> >> Notice that such constant and variables are used in contexts that >> expect expressions of type uint64_t (64 bits, unsigned). The current >> casts to uint64_t effectively apply to each expression as a whole, >> but they do not prevent them from being evaluated using 32-bit >> arithmetic instead of 64-bit arithmetic. >> >> Also, once the expressions are properly evaluated using 64-bit >> arithmentic, there is no need for the parentheses that enclose >> them. >> >> Addresses-Coverity-ID: 1460245 ("Unintentional integer overflow") >> Addresses-Coverity-ID: 1460286 ("Unintentional integer overflow") >> Addresses-Coverity-ID: 1460401 ("Unintentional integer overflow") >> Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)") >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> >> [...] >> >> @@ -145,8 +145,8 @@ static bool calculate_fb_and_fractional_fb_divider( >> * of fractional feedback decimal point and the fractional FB Divider precision >> * is 2 then the equation becomes (ullfeedbackDivider + 5*100) / (10*100))*/ >> >> - feedback_divider += (uint64_t) >> - (5 * calc_pll_cs->fract_fb_divider_precision_factor); >> + feedback_divider += 5UL * >> + calc_pll_cs->fract_fb_divider_precision_factor; > > This should be 5ULL, as the commit log says, otherwise it's still only > 32 bits on 32-bit platforms. > Agreed. Otherwise this looks good. With that fixed this patch is Reviewed-by: Harry Wentland <harry.wentland@amd.com> Harry > _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
next prev parent reply other threads:[~2018-07-04 17:51 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-04 1:13 [PATCH] drm/amd/display/dc/dce: Fix multiple potential integer overflows Gustavo A. R. Silva 2018-07-04 7:38 ` Michel Dänzer 2018-07-04 7:38 ` Michel Dänzer 2018-07-04 12:51 ` Gustavo A. R. Silva 2018-07-04 17:51 ` Harry Wentland [this message] 2018-07-04 17:51 ` Harry Wentland 2018-07-04 17:54 ` Gustavo A. R. Silva 2018-07-04 18:05 ` Harry Wentland 2018-07-04 18:05 ` Harry Wentland
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