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Date: Sat, 10 Oct 2026 16:08:58 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Tuo Li <islituo@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] lib/test_meminit: handle kmem_cache_alloc() failure
Message-Id: <20261010160858.453c904ce17dfa8868ba3f9b@linux-foundation.org>
In-Reply-To: <20261009073040.2995938-1-islituo@gmail.com>
References: <20261009073040.2995938-1-islituo@gmail.com>
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On Fri,  9 Oct 2026 15:30:40 +0800 Tuo Li <islituo@gmail.com> wrote:

> In do_kmem_cache_size(), kmem_cache_alloc() may fail and return NULL.
> The returned pointer is subsequently passed to check_buf() and
> fill_with_garbage_skip() without being checked, which may result in a
> NULL pointer dereference.
> 
> Handle the allocation failure by marking the test as failed and
> continuing with the next iteration.
> 
> ...
>
> --- a/lib/test_meminit.c
> +++ b/lib/test_meminit.c
> @@ -241,6 +241,10 @@ static int __init do_kmem_cache_size(size_t size, bool want_ctor,
>  		}
>  
>  		buf = kmem_cache_alloc(c, alloc_mask);
> +		if (!buf) {
> +			fail = true;
> +			continue;
> +		}
>  		/* Check that buf is zeroed, if it must be. */
>  		fail |= check_buf(buf, size, want_ctor, want_rcu, want_zero);
>  		fill_with_garbage_skip(buf, size, want_ctor ? CTOR_BYTES : 0);

Thanks, but we have an assumption that __init-time allocations cannot
fail and so they don't need to be checked.  Because if they do fail,
something has gone horribly wrong and this kernel cannot work and a
later null-deref of "buf" is a suitable way of reporting this.