linux-kernel - Re: [PATCH] crypto: zstd - Fix compression bug caused by truncation

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Message-ID: <20250930160940.rfb2ed4ekal4ptid@cozumel>
Date: Tue, 30 Sep 2025 11:09:40 -0500
From: Han Xu <han.xu@....com>
To: David Sterba <dsterba@...e.cz>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
	"suman.kumar.chakraborty@...el.com" <suman.kumar.chakraborty@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"terrelln@...com" <terrelln@...com>,
	"dsterba@...e.com" <dsterba@...e.com>,
	Richard Weinberger <richard@....at>,
	"chengzhihao1@...wei.com" <chengzhihao1@...wei.com>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:MEMORY TECHNOLOGY DEVICES (MTD)" <linux-mtd@...ts.infradead.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: Re: [PATCH] crypto: zstd - Fix compression bug caused by truncation

On 25/09/30 03:32PM, David Sterba wrote:
> 
> On Tue, Sep 30, 2025 at 04:08:34PM +0800, Herbert Xu wrote:
> > On Mon, Sep 29, 2025 at 11:51:36PM +0000, Han Xu wrote:
> > > Hi Suman,
> > >
> > > The patch f5ad93ffb5411 "crypto: zstd - convert to acomp"
> > > leads to the following kernel dump during UBIFS write back.
> >
> > Thanks for the detailed report and instructions!
> >
> > Please let me know if you still get the crash with this patch:
> >
> > ---8<---
> > Use size_t for the return value of zstd_compress_cctx as otherwise
> > negative errors will be truncated to a positive value.
> >
> > Reported-by: Han Xu <han.xu@....com>
> > Fixes: f5ad93ffb541 ("crypto: zstd - convert to acomp")
> > Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 
> Reviewed-by: David Sterba <dsterba@...e.com>

It works well now. Thanks for the quick fix.

Tested-by: Han Xu <han.xu@....com>

> 
> >
> > diff --git a/crypto/zstd.c b/crypto/zstd.c
> > index c2a19cb0879d..ac318d333b68 100644
> > --- a/crypto/zstd.c
> > +++ b/crypto/zstd.c
> > @@ -83,7 +83,7 @@ static void zstd_exit(struct crypto_acomp *acomp_tfm)
> >  static int zstd_compress_one(struct acomp_req *req, struct zstd_ctx *ctx,
> >                            const void *src, void *dst, unsigned int *dlen)
> >  {
> > -     unsigned int out_len;
> > +     size_t out_len;
> >
> >       ctx->cctx = zstd_init_cctx(ctx->wksp, ctx->wksp_size);
> >       if (!ctx->cctx)
> > --