[PATCH 36/46] mm: fix unkillable fault loop on MAP_DROPPABLE memory

[sashiko-bot at kernel.org]

> From: Chris Mason <mason at kernel.org>
> 
> handle_mm_fault() suppresses VM_FAULT_OOM for VM_DROPPABLE mappings.
> 
> For user-mode faults, pending signals are processed before retrying the
> access. Kernel-mode faults on user buffers instead return directly to
> the faulting instruction.
> 
> With persistent allocation failures (esp. memcg limits), a syscall,
> such as write(), can therefore loop while not dropping locks.
> 
> Only suppress VM_FAULT_OOM when FAULT_FLAG_USER is set, allowing
> kernel-mode faults and GUP to fail and signal allocation errors.
> 
> Fix generated by an LLM and sent by Chris Mason in private.
> 
> Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings")
> Cc: stable at vger.kernel.org
> Signed-off-by: Chris Mason <mason at kernel.org>
> Reviewed-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
> [ david: simplify description ]
> Signed-off-by: David Hildenbrand (Arm) <david at kernel.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org?part=36