linux-kernel - Re: [PATCH] zswap: do not crash the kernel on decompression failure

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Message-Id: <20250225142518.cec35a0ea77a0d86f3e860c3@linux-foundation.org>
Date: Tue, 25 Feb 2025 14:25:18 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Nhat Pham <nphamcs@...il.com>
Cc: hannes@...xchg.org, yosryahmed@...gle.com, chengming.zhou@...ux.dev,
 linux-mm@...ck.org, kernel-team@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zswap: do not crash the kernel on decompression failure

On Tue, 25 Feb 2025 13:32:00 -0800 Nhat Pham <nphamcs@...il.com> wrote:

> @@ -984,12 +987,19 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
>  	sg_init_table(&output, 1);
>  	sg_set_folio(&output, folio, PAGE_SIZE, 0);
>  	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, PAGE_SIZE);
> -	BUG_ON(crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait));
> -	BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
> +	if (crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait) ||
> +			acomp_ctx->req->dlen != PAGE_SIZE) {
> +		ret = false;
> +		zswap_reject_decompress_fail++;
> +		pr_alert_ratelimited(
> +			"decompression failed on zswap entry with offset %08lx\n",
> +			entry->swpentry.val);
> +	}
>  	mutex_unlock(&acomp_ctx->mutex);

This mutex_unlock() isn't present in current kernels.  I'd normally just fix
the reject but a change in the locking environment needs some careful
checking and retesting, please.