linux-kernel - Re: [PATCH -next] fanotify: Fix the checks in fanotify_fsid

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Message-ID: <20200330104045.GA26544@quack2.suse.cz>
Date:   Mon, 30 Mar 2020 12:40:45 +0200
From:   Jan Kara <jack@...e.cz>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH -next] fanotify: Fix the checks in fanotify_fsid_equal

On Fri 27-03-20 10:10:30, Nathan Chancellor wrote:
> Clang warns:
> 
> fs/notify/fanotify/fanotify.c:28:23: warning: self-comparison always
> evaluates to true [-Wtautological-compare]
>         return fsid1->val[0] == fsid1->val[0] && fsid2->val[1] == fsid2->val[1];
>                              ^
> fs/notify/fanotify/fanotify.c:28:57: warning: self-comparison always
> evaluates to true [-Wtautological-compare]
>         return fsid1->val[0] == fsid1->val[0] && fsid2->val[1] == fsid2->val[1];
>                                                                ^
> 2 warnings generated.
> 
> The intention was clearly to compare val[0] and val[1] in the two
> different fsid structs. Fix it otherwise this function always returns
> true.
> 
> Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
> Link: https://github.com/ClangBuiltLinux/linux/issues/952
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Thanks for the fix! That's a good catch that would have been pain to debug!
I've applied it to my tree.

								Honza

> ---
>  fs/notify/fanotify/fanotify.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 7a889da1ee12..cb54ecdb3fb9 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -25,7 +25,7 @@ static bool fanotify_path_equal(struct path *p1, struct path *p2)
>  static inline bool fanotify_fsid_equal(__kernel_fsid_t *fsid1,
>  				       __kernel_fsid_t *fsid2)
>  {
> -	return fsid1->val[0] == fsid1->val[0] && fsid2->val[1] == fsid2->val[1];
> +	return fsid1->val[0] == fsid2->val[0] && fsid1->val[1] == fsid2->val[1];
>  }
>  
>  static bool fanotify_fh_equal(struct fanotify_fh *fh1,
> -- 
> 2.26.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR