linux-kernel - Re: [PATCH] tools/power x86_energy_perf_policy: Fix potential NULL pointer dereference

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Message-ID: <CAJvTdKkMfOYsj_9YeBodPXs8pLgy6OcYXK32ffqOAn2kDo=ZKQ@mail.gmail.com>
Date: Tue, 25 Nov 2025 12:23:05 -0500
From: Len Brown <lenb@...nel.org>
To: Malaya Kumar Rout <mrout@...hat.com>
Cc: linux-kernel@...r.kernel.org, malayarout91@...il.com, 
	Len Brown <len.brown@...el.com>, Kaushlendra Kumar <kaushlendra.kumar@...el.com>
Subject: Re: [PATCH] tools/power x86_energy_perf_policy: Fix potential NULL
 pointer dereference

I've applied these two patches, thanks.

BTW. we generally use the linux-pm list for patches to these utilities
rather than lkml -- as we manage the patches there via patchwork.

-Len

On Sat, Nov 22, 2025 at 10:17 AM Malaya Kumar Rout <mrout@...hat.com> wrote:
>
> In err_on_hypervisor(), strstr() is called to search for "flags" in the
> buffer, but the return value is not checked before being used in pointer
> arithmetic (flags - buffer). If strstr() returns NULL because "flags" is
> not found in /proc/cpuinfo, this will cause undefined behavior and likely
> a crash.
>
> Add a NULL check after the strstr() call and handle the error appropriately
> by cleaning up resources and reporting a meaningful error message.
>
> Signed-off-by: Malaya Kumar Rout <mrout@...hat.com>
> ---
>  .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c      | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
> index 884a4c746f32..be2a9c285a85 100644
> --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
> +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
> @@ -660,6 +660,11 @@ void err_on_hypervisor(void)
>         }
>
>         flags = strstr(buffer, "flags");
> +       if (!flags) {
> +               fclose(cpuinfo);
> +               free(buffer);
> +               err(1, "Failed to find 'flags' in /proc/cpuinfo");
> +       }
>         rewind(cpuinfo);
>         fseek(cpuinfo, flags - buffer, SEEK_SET);
>         if (!fgets(buffer, 4096, cpuinfo)) {
> --
> 2.51.0
>
>


-- 
Len Brown, Intel Open Source Technology Center