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")

Signed-off-by: luofei <luofei@unicloud.com>
Cc: stable@vger.kernel.org #v4.14
---
 arch/x86/kernel/cpu/mcheck/mce.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 95c09db1bba2..d8399a689165 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -589,7 +589,7 @@ 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;
-		if (memory_failure(pfn, MCE_VECTOR, 0))
+		if (!memory_failure(pfn, MCE_VECTOR, 0))
 			mce_unmap_kpfn(pfn);
 	}
 
-- 
2.27.0

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.

thanks,

greg k-h

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

On Mon, Feb 07, 2022 at 10:35:41AM +0100, Borislav Petkov wrote:
> 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;
> 

Ah, ok, if so, this needs to be documented really really well in the
changelog text so no one is confused.  Like me :)

thanks,

greg k-h