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SubjectRe: [PATCH] x86/apic: fix integer overflow on 10 bit right shift of cpu_khz
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On 19/06/2019 19:13, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> The right shift of unsigned int cpu_khz will overflow for large values
> of cpu_khz, so cast it to a long long before shifting it to avoid
> overvlow. For example, this can happen when cpu_khz is 4194305 (just
> less than 4.2 GHz). Also wrap line to avoid checkpatch wide line
> warning.
>
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: 8c3ba8d04924 ("x86, apic: ack all pending irqs when crashed/on kexec")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> arch/x86/kernel/apic/apic.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 8956072f677d..31426126e5e0 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -1464,7 +1464,8 @@ static void apic_pending_intr_clear(void)
> if (queued) {
> if (boot_cpu_has(X86_FEATURE_TSC) && cpu_khz) {
> ntsc = rdtsc();
> - max_loops = (cpu_khz << 10) - (ntsc - tsc);
> + max_loops = ((long long)cpu_khz << 10) -
> + (ntsc - tsc);
> } else {
> max_loops--;
> }
>
Nack. V2 coming next.

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