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

[Nhat Pham]

On Tue, Feb 25, 2025 at 2:25 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, 25 Feb 2025 13:32:00 -0800 Nhat Pham <nphamcs@xxxxxxxxx> 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.

Hah strange. I could have sworn I pulled the latest mm-unstable, but
maybe the git pull failed and I didn't notice. Thanks for picking this
up Andrew! Lemme re-pull and rebase.