linux-kernel - Re: [PATCH] x86/mm, mm/hwpoison: fix unmap kernel 1:1 pages

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Message-ID: <YgDn7WWdcD5xaprX@zn.tnic>
Date:   Mon, 7 Feb 2022 10:35:41 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     luofei <luofei@...cloud.com>, stable@...r.kernel.org,
        tony.luck@...el.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm, mm/hwpoison: fix unmap kernel 1:1 pages

On Mon, Feb 07, 2022 at 09:14:23AM +0100, Greg KH wrote:
> On Mon, Feb 07, 2022 at 02:52:42AM -0500, luofei wrote:
> > Only unmap the page when the memory error is properly handled
> > by calling memory_failure(), not the other way around.
> > 
> > Fixes: 26f8c38bb466("x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages")
> 
> This commit is not in Linus's tree.  Please use the correct commit id.

I think he's trying to fix the backport:

see 26f8c38bb466c1a2d232d7609fb4bfb4bc121678 which is the stable tree backport:

@@ -582,7 +586,8 @@ static int srao_decode_notifier(struct notifier_block *nb, unsigned long val,
 
        if (mce_usable_address(mce) && (mce->severity == MCE_AO_SEVERITY)) {
                pfn = mce->addr >> PAGE_SHIFT;
-               memory_failure(pfn, MCE_VECTOR, 0);
+               if (memory_failure(pfn, MCE_VECTOR, 0))
+                       mce_unmap_kpfn(pfn);
        }


vs the upstream commit:

fd0e786d9d09024f67bd71ec094b110237dc3840

@@ -590,7 +594,8 @@ static int srao_decode_notifier(struct notifier_block *nb, unsigned long val,
 
        if (mce_usable_address(mce) && (mce->severity == MCE_AO_SEVERITY)) {
                pfn = mce->addr >> PAGE_SHIFT;
-               memory_failure(pfn, 0);
+               if (!memory_failure(pfn, 0))
+                       mce_unmap_kpfn(pfn);
        }
 
        return NOTIFY_OK;

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette