linux-kernel - Re: [PATCH] x86/pm: Fix false positive kmemleak report in msr_build

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Date: Thu, 14 Mar 2024 08:05:35 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Anton Altaparmakov <anton@...era.com>,
 "Rafael J . Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@....cz>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
 Chen Yu <yu.c.chen@...el.com>
Cc: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
 Catalin Marinas <catalin.marinas@....com>, linux-mm@...ck.org,
 Matthieu Baerts <matthieu.baerts@...sares.net>,
 Mat Martineau <mathew.j.martineau@...ux.intel.com>,
 "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
 Ingo Molnar <mingo@...nel.org>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] x86/pm: Fix false positive kmemleak report in
 msr_build_context().

On 3/14/24 07:26, Anton Altaparmakov wrote:
>  /* image of the saved processor state */
>  struct saved_context {
> -	/*
> -	 * On x86_32, all segment registers except gs are saved at kernel
> -	 * entry in pt_regs.
> -	 */
> -	u16 gs;
>  	unsigned long cr0, cr2, cr3, cr4;
>  	u64 misc_enable;
>  	struct saved_msrs saved_msrs;
> @@ -27,6 +22,11 @@ struct saved_context {
>  	unsigned long tr;
>  	unsigned long safety;
>  	unsigned long return_address;
> +	/*
> +	 * On x86_32, all segment registers except gs are saved at kernel
> +	 * entry in pt_regs.
> +	 */
> +	u16 gs;
>  	bool misc_enable_saved;
>  } __attribute__((packed));

Isn't this just kinda poking at the symptoms?  This seems to be
basically the exact same bug as b0b592cf08, just with a different source
of unaligned structure members.

There's nothing to keep folks from reintroducing these kinds of issues
and evidently no way to detect when they happen without lengthy reproducers.