diff options
| author | Zhan Xusheng <zhanxusheng1024@gmail.com> | 2026-06-16 19:20:17 +0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@kernel.org> | 2026-06-17 17:58:34 +0200 |
| commit | 26aff38fefb1d6cd87e22525f41cc8f1aa61b24f (patch) | |
| tree | b80bcf0d2dbc5ec3e75c23e95f3a3143718ac433 /kernel/time | |
| parent | 8fa30821180a9a19e78e9f4df1c0ba710252801e (diff) | |
posix-cpu-timers: Use u64 multiplication in update_rlimit_cpu()
update_rlimit_cpu() converts the RLIMIT_CPU value to nanoseconds with
u64 nsecs = rlim_new * NSEC_PER_SEC;
On 32-bit kernels both rlim_new (unsigned long) and NSEC_PER_SEC
(1000000000L) are 32-bit, so the multiplication is performed in unsigned
long and truncated for rlim_new > 4 seconds before being widened to u64.
The same file already casts to u64 for the matching computation in
check_process_timers():
u64 softns = (u64)soft * NSEC_PER_SEC;
As a result, the truncated value is installed into the CPUCLOCK_PROF
expiry cache (nextevt), causing the process CPU timer to be programmed
to fire prematurely for any RLIMIT_CPU soft limit >= 5 seconds. The
actual SIGXCPU/SIGKILL decision in check_process_timers() already casts
to u64 and is therefore correct, so limit enforcement is not broken;
only the expiry-cache programming is wrong. Apply the same cast here so
both paths convert rlim_cur identically.
64-bit kernels are unaffected.
Fixes: 858cf3a8c599 ("timers/itimer: Convert internal cputime_t units to nsec")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260616112017.1681372-1-zhanxusheng@xiaomi.com
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 74775b94d11b..5e633d8750d1 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -41,7 +41,7 @@ void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit) */ int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) { - u64 nsecs = rlim_new * NSEC_PER_SEC; + u64 nsecs = (u64)rlim_new * NSEC_PER_SEC; unsigned long irq_fl; if (!lock_task_sighand(task, &irq_fl)) |