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

[Suman Kumar Chakraborty]

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:

Thank you Herbert. It fixes the issue.

> 
> ---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 at nxp.com>
> Fixes: f5ad93ffb541 ("crypto: zstd - convert to acomp")
> Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
> 
> 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)
> -- 
> Email: Herbert Xu <herbert at gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt