Date:   Wed, 15 Mar 2023 11:16:31 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Jason Wessel <jason.wessel@windriver.com>,
        "Daniel Thompson" <daniel.thompson@linaro.org>,
        Douglas Anderson <dianders@chromium.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>,
        Petr Mladek <pmladek@suse.com>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Chris Down <chris@chrisdown.name>,
        Nick Terrell <terrelln@fb.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, <linux-modules@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <kgdb-bugreport@lists.sourceforge.net>,
        <live-patching@vger.kernel.org>, <bpf@vger.kernel.org>,
        <llvm@lists.linux.dev>
CC:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
        Piotr Gorski <piotrgorski@cachyos.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Ira Weiny <ira.weiny@intel.com>
Subject: Re: [PATCH] module/decompress: Never use kunmap() for local
 un-mappings
Message-ID: <64120b7f2e123_2513fa294a7@iweiny-mobl.notmuch>
References: <20230315125256.22772-1-fmdefrancesco@gmail.com>
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Fabio M. De Francesco wrote:
> Use kunmap_local() to unmap pages locally mapped with kmap_local_page().
> 
> kunmap_local() must be called on the kernel virtual address returned by
> kmap_local_page(), differently from how we use kunmap() which instead
> expects the mapped page as its argument.
> 
> In module_zstd_decompress() we currently map with kmap_local_page() and
> unmap with kunmap(). This breaks the code and so it should be fixed.
> 
> Cc: Piotr Gorski <piotrgorski@cachyos.org>
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: Luis Chamberlain <mcgrof@kernel.org>
> Cc: Stephen Boyd <swboyd@chromium.org>
> Cc: Ira Weiny <ira.weiny@intel.com>

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> Fixes: 169a58ad824d ("module/decompress: Support zstd in-kernel decompression")
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> ---
>  kernel/module/decompress.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/module/decompress.c b/kernel/module/decompress.c
> index bb79ac1a6d8f..7ddc87bee274 100644
> --- a/kernel/module/decompress.c
> +++ b/kernel/module/decompress.c
> @@ -267,7 +267,7 @@ static ssize_t module_zstd_decompress(struct load_info *info,
>  		zstd_dec.size = PAGE_SIZE;
>  
>  		ret = zstd_decompress_stream(dstream, &zstd_dec, &zstd_buf);
> -		kunmap(page);
> +		kunmap_local(zstd_dec.dst);
>  		retval = zstd_get_error_code(ret);
>  		if (retval)
>  			break;
> -- 
> 2.39.2
>