linux-kernel - Re: [PATCH] eventfs: Use ERR_CAST() in eventfs_create_events

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Message-ID: <202310181114.55457CFE@keescook>
Date:   Wed, 18 Oct 2023 11:14:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     rostedt@...dmis.org, mhiramat@...nel.org, ndesaulniers@...gle.com,
        trix@...hat.com, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev
Subject: Re: [PATCH] eventfs: Use ERR_CAST() in eventfs_create_events_dir()

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@...nel.org>

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

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

-- 
Kees Cook