Re: [PATCH] mm: kvmalloc: Bail if called with soft or hard IRQs disabled

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] mm: kvmalloc: commit message mismatch and deprecated
  in_interrupt() use
--

commit bac4fc34f0010889bd9f7724714bf23ec9386ed9
Author: Herbert Xu <herbert@gondor.apana.org.au>

> mm: kvmalloc: Bail if called with soft or hard IRQs disabled
>
> On Thu, Nov 05, 2026 at 06:37:49PM +0100, Uladzislau Rezki wrote:
> >
> > Probably the simplest option is to return NULL for non-blocking vmalloc()
> > allocations when BH are disabled. That would address the reported
> > rhashtable deadlock.
>
> OK let's try this patch:
>
> ---8<---
> The function kvmalloc may call vmalloc under the hood even when
> used with GFP_ATOMIC.  However, vmalloc uses naked spin locks so
> it must not be called if the caller already holds spin locks that
> can be used in hard or soft IRQ context.
>
> Use the heuristic irqs_disabled() || in_softirq() to detect such
> callers and prevent them from using vmalloc.
>
> Reported-by: Liam R. Howlett (Google) <liam@infradead.org>
> Fixes: c6307674ed82 ("mm: kvmalloc: add non-blocking support for vmalloc")
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a151268b97263..5965d69926154 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -7148,6 +7148,14 @@ void *__kvmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), unsigned long
>  	if (ret || size <= PAGE_SIZE)
>  		return ret;
>  
> +	/*
> +	 * vmalloc uses naked spin locks, so it must not be used if
> +	 * the caller already holds a spin lock that can be used in
> +	 * a soft or hard IRQ.  Use heuristics to detect this.
> +	 */
> +	if (irqs_disabled() || in_interrupt())
> +		return NULL;

[Severity: Low]
The commit message says this uses irqs_disabled() || in_softirq(), whereas
__kvmalloc_node_noprof() calls in_interrupt().  Note that both in_softirq()
and in_interrupt() are marked deprecated in include/linux/preempt.h and
documented as not to be used in new code.  Also, the commit message still
contains the unstripped email reply preamble and "---8<---" scissors line.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/avcKfEvln8_2a7fJ@gondor.apana.org.au?part=1