Re: [PATCH] hw/misc: cast rpm to uint64_t

[Hao Wu]

On Fri, Dec 27, 2024 at 3:02 AM Patrick Leis <venture@google.com> wrote:

On Thu, Dec 26, 2024 at 6:00 AM Tigran Sogomonian <tsogomonian@astralinux.ru> wrote:

The value of an arithmetic _expression_
'rpm * NPCM7XX_MFT_PULSE_PER_REVOLUTION' is a subject
to overflow because its operands are not cast to
a larger data type before performing arithmetic. Thus, need
to cast rpm to uint64_t.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Tigran Sogomonian <tsogomonian@astralinux.ru>

Reviewed-by: Patrick Leis <venture@google.com> 

Reviewed-by: Hao Wu <wuhaotsh@google.com> 

---
 hw/misc/npcm7xx_mft.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/misc/npcm7xx_mft.c b/hw/misc/npcm7xx_mft.c
index 9fcc69fe5c..e565cac05d 100644
--- a/hw/misc/npcm7xx_mft.c
+++ b/hw/misc/npcm7xx_mft.c
@@ -172,8 +172,9 @@ static NPCM7xxMFTCaptureState npcm7xx_mft_compute_cnt(
          * RPM = revolution/min. The time for one revlution (in ns) is
          * MINUTE_TO_NANOSECOND / RPM.
          */
-        count = clock_ns_to_ticks(clock, (60 * NANOSECONDS_PER_SECOND) /
-            (rpm * NPCM7XX_MFT_PULSE_PER_REVOLUTION));
+        count = clock_ns_to_ticks(clock,
+            (uint64_t)(60 * NANOSECONDS_PER_SECOND) /
+            ((uint64_t)rpm * NPCM7XX_MFT_PULSE_PER_REVOLUTION));
     }

     if (count > NPCM7XX_MFT_MAX_CNT) {
--
2.30.2