| Message ID | 20181005133012.26490-1-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | hw/display/bcm2835_fb: Silence Coverity warning about multiply overflow | expand |
On 05/10/2018 15:30, Peter Maydell wrote: > Coverity complains (CID 1395628) that the multiply in the calculation > of the framebuffer base is performed as 32x32 but then used in a > context that takes a 64-bit hwaddr. This can't actually ever > overflow the 32-bit result, because of the constraints placed on > the s->config values in bcm2835_fb_validate_config(). But we > can placate Coverity anyway, by explicitly casting one of the > inputs to a hwaddr, so the whole expression is calculated with > 64-bit arithmetic. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > This is one of those cases where I was 50/50 about whether to just > mark the coverity issue as a false-positive. Agreed, but in the end it's not too much noise, so Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Thanks, Paolo > hw/display/bcm2835_fb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/display/bcm2835_fb.c b/hw/display/bcm2835_fb.c > index d534d00a65f..599863e4e17 100644 > --- a/hw/display/bcm2835_fb.c > +++ b/hw/display/bcm2835_fb.c > @@ -190,7 +190,7 @@ static void fb_update_display(void *opaque) > } > > if (s->invalidate) { > - hwaddr base = s->config.base + xoff + yoff * src_width; > + hwaddr base = s->config.base + xoff + (hwaddr)yoff * src_width; > framebuffer_update_memory_section(&s->fbsection, s->dma_mr, > base, > s->config.yres, src_width); >
diff --git a/hw/display/bcm2835_fb.c b/hw/display/bcm2835_fb.c index d534d00a65f..599863e4e17 100644 --- a/hw/display/bcm2835_fb.c +++ b/hw/display/bcm2835_fb.c @@ -190,7 +190,7 @@ static void fb_update_display(void *opaque) } if (s->invalidate) { - hwaddr base = s->config.base + xoff + yoff * src_width; + hwaddr base = s->config.base + xoff + (hwaddr)yoff * src_width; framebuffer_update_memory_section(&s->fbsection, s->dma_mr, base, s->config.yres, src_width);
Coverity complains (CID 1395628) that the multiply in the calculation of the framebuffer base is performed as 32x32 but then used in a context that takes a 64-bit hwaddr. This can't actually ever overflow the 32-bit result, because of the constraints placed on the s->config values in bcm2835_fb_validate_config(). But we can placate Coverity anyway, by explicitly casting one of the inputs to a hwaddr, so the whole expression is calculated with 64-bit arithmetic. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- This is one of those cases where I was 50/50 about whether to just mark the coverity issue as a false-positive. hw/display/bcm2835_fb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.19.0