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Message-ID: <70261e2a-b87e-462e-964e-95a51ecde978@intel.com>
Date: Thu, 14 Mar 2024 08:05:35 -0700
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Subject: Re: [PATCH] x86/pm: Fix false positive kmemleak report in
 msr_build_context().
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To: Anton Altaparmakov <anton@tuxera.com>,
 "Rafael J . Wysocki" <rafael@kernel.org>, Pavel Machek <pavel@ucw.cz>,
 Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
 Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>,
 x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
 Chen Yu <yu.c.chen@intel.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
 Catalin Marinas <catalin.marinas@arm.com>, linux-mm@kvack.org,
 Matthieu Baerts <matthieu.baerts@tessares.net>,
 Mat Martineau <mathew.j.martineau@linux.intel.com>,
 "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
 Ingo Molnar <mingo@kernel.org>, linux-pm@vger.kernel.org,
 linux-kernel@vger.kernel.org, stable@vger.kernel.org
References: <20240314142656.17699-1-anton@tuxera.com>
From: Dave Hansen <dave.hansen@intel.com>
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In-Reply-To: <20240314142656.17699-1-anton@tuxera.com>
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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.