Re: [PATCH 1/2] mm/page_alloc: don't spin_trylock() in NMI on UP

[Harry Yoo]

On 7/15/26 6:03 PM, Brendan Jackman wrote:
> As noted in can_spin_trylock(), using this is unsafe in this context.
> commit 620b46ed6ae17 ("mm/page_alloc: return NULL early from
> alloc_frozen_pages_nolock() in NMI on UP") fixed this on the alloc side
> but missed the free side.
> 
> Impact: If BPF programs using these features in NMI (probably tracing)
> are present on non-SMP builds this might crash the kernel and is
> probably exploitable by local attackers for privilege escalation.
> 
> Reported-by: sashiko-bot@xxxxxxxxxx
> Link: https://sashiko.dev/#/patchset/20260703-alloc-trylock-v5-0-c87b714e19d3%40google.com?part=18
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 8c57b687e8331 ("mm, bpf: Introduce free_pages_nolock()")
> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
> ---

Looks good to me, so:
Reviewed-by: Harry Yoo (Oracle) <harry@xxxxxxxxxx>

-- 
Cheers,
Harry / Hyeonggon

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