[PATCH] drm/msm: Avoid potential overflow in timeout_to_jiffies()
Dmitry Baryshkov
dmitry.baryshkov at linaro.org
Fri Oct 1 17:17:43 UTC 2021
On 17/09/2021 03:59, Marek Vasut wrote:
> The return type of ktime_divns() is s64. The timeout_to_jiffies() currently
> assigns the result of this ktime_divns() to unsigned long, which on 32 bit
> systems may overflow. Furthermore, the result of this function is sometimes
> also passed to functions which expect signed long, dma_fence_wait_timeout()
> is one such example.
>
> Fix this by adjusting the type of remaining_jiffies to s64, so we do not
> suffer overflow there, and return a value limited to range of 0..INT_MAX,
> which is safe for all usecases of this timeout.
>
> The above overflow can be triggered if userspace passes in too large timeout
> value, larger than INT_MAX / HZ seconds. The kernel detects it and complains
> about "schedule_timeout: wrong timeout value %lx" and generates a warning
> backtrace.
>
> Note that this fixes commit 6cedb8b377bb ("drm/msm: avoid using 'timespec'"),
> because the previously used timespec_to_jiffies() function returned unsigned
> long instead of s64:
> static inline unsigned long timespec_to_jiffies(const struct timespec *value)
>
> Fixes: 6cedb8b377bb ("drm/msm: avoid using 'timespec'")
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: Jordan Crouse <jcrouse at codeaurora.org>
> Cc: Rob Clark <robdclark at chromium.org>
> Cc: stable at vger.kernel.org # 5.6+
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> ---
> NOTE: This is related to Mesa MR
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12886
> ---
> drivers/gpu/drm/msm/msm_drv.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 0b2686b060c73..d96b254b8aa46 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -543,7 +543,7 @@ static inline int align_pitch(int width, int bpp)
> static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
> {
> ktime_t now = ktime_get();
> - unsigned long remaining_jiffies;
> + s64 remaining_jiffies;
>
> if (ktime_compare(*timeout, now) < 0) {
> remaining_jiffies = 0;
> @@ -552,7 +552,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
> remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
> }
>
> - return remaining_jiffies;
> + return clamp(remaining_jiffies, 0LL, (s64)INT_MAX);
> }
>
> #endif /* __MSM_DRV_H__ */
>
--
With best wishes
Dmitry
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