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sched/debug: Fix fair_server_period_max value

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This code has an integer overflow or sign extension bug which was caught
by gcc-13:

  kernel/sched/debug.c:341:57: error: integer overflow in expression of
  type 'long int' results in '-100663296' [-Werror=overflow]
    341 | static unsigned long fair_server_period_max = (1 << 22) * NSEC_PER_USEC; /* ~4 seconds */

The result is that "fair_server_period_max" is set to 0xfffffffffa000000
(585 years) instead of instead of 0xfa000000 (4 seconds) that was
intended.

Fix this by changing the type to shift from (1 << 22) to (1UL << 22).

Closes: https://lore.kernel.org/all/CA+G9fYtE2GAbeqU+AOCffgo2oH0RTJUxU+=Pi3cFn4di_KgBAQ@mail.gmail.com/
Fixes: d741f297bc ("sched/fair: Fair server interface")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reported-by: Arnd Bergmann <arnd@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/a936b991-e464-4bdf-94ab-08e25d364986@stanley.mountain
This commit is contained in:
Dan Carpenter 2024-08-01 10:44:03 -05:00 committed by Peter Zijlstra
parent 924e2904da
commit 4ae0c2b911
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/debug.c
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@ -338,7 +338,7 @@ enum dl_param {
DL_PERIOD,
};
static unsigned long fair_server_period_max = (1 << 22) * NSEC_PER_USEC; /* ~4 seconds */
static unsigned long fair_server_period_max = (1UL << 22) * NSEC_PER_USEC; /* ~4 seconds */
static unsigned long fair_server_period_min = (100) * NSEC_PER_USEC; /* 100 us */
static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubuf,