linux-hardening - Re: [PATCH] ALSA: seq: Fix function prototype mismatch in snd_seq_expand_var

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Date:   Sat, 19 Nov 2022 09:20:53 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     Jaroslav Kysela <perex@...ex.cz>,
        kernel test robot <lkp@...el.com>,
        Takashi Iwai <tiwai@...e.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        alsa-devel@...a-project.org, Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ALSA: seq: Fix function prototype mismatch in snd_seq_expand_var_event

On Sat, 19 Nov 2022 00:23:50 +0100,
Kees Cook wrote:
> 
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed.
> 
> seq_copy_in_user() and seq_copy_in_kernel() did not have prototypes
> matching snd_seq_dump_func_t. Adjust this and remove the casts. There
> are not resulting binary output differences.
> 
> This was found as a result of Clang's new -Wcast-function-type-strict
> flag, which is more sensitive than the simpler -Wcast-function-type,
> which only checks for type width mismatches.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Link: https://lore.kernel.org/lkml/202211041527.HD8TLSE1-lkp@intel.com
> Cc: Jaroslav Kysela <perex@...ex.cz>
> Cc: Takashi Iwai <tiwai@...e.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: alsa-devel@...a-project.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Thanks, applied.


Takashi