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Date:   Wed, 18 Oct 2023 11:14:22 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     rostedt@goodmis.org, mhiramat@kernel.org, ndesaulniers@google.com,
        trix@redhat.com, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, llvm@lists.linux.dev,
        patches@lists.linux.dev
Subject: Re: [PATCH] eventfs: Use ERR_CAST() in eventfs_create_events_dir()
Message-ID: <202310181114.55457CFE@keescook>
References: <20231018-ftrace-fix-clang-randstruct-v1-1-338cb214abfb@kernel.org>
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On Wed, Oct 18, 2023 at 11:10:31AM -0700, Nathan Chancellor wrote:
> When building with clang and CONFIG_RANDSTRUCT_FULL=y, there is an error
> due to a cast in eventfs_create_events_dir():
> 
>   fs/tracefs/event_inode.c:734:10: error: casting from randomized structure pointer type 'struct dentry *' to 'struct eventfs_inode *'
>     734 |                 return (struct eventfs_inode *)dentry;
>         |                        ^
>   1 error generated.
> 
> Use the ERR_CAST() function to resolve the error, as it was designed for
> this exact situation (casting an error pointer to another type).
> 
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1947
> Fixes: 5790b1fb3d67 ("eventfs: Remove eventfs_file and just use eventfs_inode")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Yes, please. That's the correct method to do such casts. Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook