Re: [PATCH v3 1/3] mm/memory-failure: Use a mutex to avoid memory_failure() races

[Borislav Petkov]

On Wed, Apr 21, 2021 at 09:57:26AM +0900, Naoya Horiguchi wrote:
> From: Tony Luck <tony.luck@xxxxxxxxx>
> 
> There can be races when multiple CPUs consume poison from the same
> page. The first into memory_failure() atomically sets the HWPoison
> page flag and begins hunting for tasks that map this page. Eventually
> it invalidates those mappings and may send a SIGBUS to the affected
> tasks.
> 
> But while all that work is going on, other CPUs see a "success"
> return code from memory_failure() and so they believe the error
> has been handled and continue executing.
> 
> Fix by wrapping most of the internal parts of memory_failure() in
> a mutex.
> 
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> ---
>  mm/memory-failure.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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