Re: [PATCH] mm/memfd_luo: validate serialized_data before conversion

[Mike Rapoport <rppt@kernel.org>]

On Thu, Jun 11, 2026 at 03:37:12PM +0200, Pratyush Yadav wrote:
> On Thu, Jun 11 2026, Mike Rapoport wrote:
> 
> > On Thu, Jun 11, 2026 at 10:30:03AM +0000, Tarun Sahu wrote:
> >> In memfd_luo_finish() and memfd_luo_retrieve(), phys_to_virt() was called
> >> on args->serialized_data before checking if the physical address is valid.
> >> Since physical address 0 does not map to virtual NULL (due to direct
> >> mapping offsets), the subsequent check 'if (!ser)' was ineffective at
> >> catching a missing serialized_data, leading to unsafe dereferences later.
> >> 
> >> Validate that args->serialized_data is non-zero before calling
> >> phys_to_virt().
> >> 
> >> Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd")
> >> Signed-off-by: Tarun Sahu <tarunsahu@google.com>
> >> ---
> >>  mm/memfd_luo.c | 10 ++++++----
> >>  1 file changed, 6 insertions(+), 4 deletions(-)
> >> 
> >> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
> >> index 59de210bee5f..10f3983b0060 100644
> >> --- a/mm/memfd_luo.c
> >> +++ b/mm/memfd_luo.c
> >> @@ -397,10 +397,11 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
> >>  	if (args->retrieve_status)
> >>  		return;
> >>  
> >> -	ser = phys_to_virt(args->serialized_data);
> >> -	if (!ser)
> >> +	if (!args->serialized_data)
> >
> > We really should make args->serialized_data a KHOSER_PTR
> 
> Hmm, that would also be a good idea. I suppose then it would be a better
> to directly convert to using KHOSER_PTR() instead of this patch?

Makes sense.
 
> -- 
> Regards,
> Pratyush Yadav

-- 
Sincerely yours,
Mike.