4.14-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit d18539754d97876503275efc7d00a1901bb0cfad ]
As reported by Meelis Roos, my previous patch causes an incorrect calculation of the timeout, through an undefined signed integer overflow:
[ 12.228155] UBSAN: Undefined behaviour in drivers/scsi/aacraid/commsup.c:2514:49 [ 12.228229] signed integer overflow: [ 12.228283] 964297611 * 250 cannot be represented in type 'long int'
The problem is that doing a multiplication with HZ first and then dividing by USEC_PER_SEC worked correctly for 32-bit microseconds, but not for 32-bit nanoseconds, which would require up to 41 bits.
This reworks the calculation to first convert the nanoseconds into jiffies, which should give us the same result as before and not overflow.
Unfortunately I did not understand the exact intention of the algorithm, in particular the part where we add half a second, so it's possible that there is still a preexisting problem in this function. I added a comment that this would be handled more nicely using usleep_range(), which generally works better for waking up at a particular time than the current schedule_timeout() based implementation. I did not feel comfortable trying to implement that without being sure what the intent is here though.
Fixes: 820f18865912 ("scsi: aacraid: use timespec64 instead of timeval") Tested-by: Meelis Roos mroos@linux.ee Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/aacraid/commsup.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c index 998788a967be..3e38bae6ecde 100644 --- a/drivers/scsi/aacraid/commsup.c +++ b/drivers/scsi/aacraid/commsup.c @@ -2506,8 +2506,8 @@ int aac_command_thread(void *data) /* Synchronize our watches */ if (((NSEC_PER_SEC - (NSEC_PER_SEC / HZ)) > now.tv_nsec) && (now.tv_nsec > (NSEC_PER_SEC / HZ))) - difference = (((NSEC_PER_SEC - now.tv_nsec) * HZ) - + NSEC_PER_SEC / 2) / NSEC_PER_SEC; + difference = HZ + HZ / 2 - + now.tv_nsec / (NSEC_PER_SEC / HZ); else { if (now.tv_nsec > NSEC_PER_SEC / 2) ++now.tv_sec; @@ -2531,6 +2531,10 @@ int aac_command_thread(void *data) if (kthread_should_stop()) break;
+ /* + * we probably want usleep_range() here instead of the + * jiffies computation + */ schedule_timeout(difference);
if (kthread_should_stop())