linux-kernel - Re: [PATCH -next] io_uring: Ensure mask is initialized in io_arm_poll

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Message-ID: <afe86a1d-dcc4-856e-48ea-f12761036e98@kernel.dk>
Date:   Mon, 2 Mar 2020 16:12:48 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH -next] io_uring: Ensure mask is initialized in
 io_arm_poll_handler

On 3/2/20 4:01 PM, Nathan Chancellor wrote:
> Clang warns:
> 
> fs/io_uring.c:4178:6: warning: variable 'mask' is used uninitialized
> whenever 'if' condition is false [-Wsometimes-uninitialized]
>         if (def->pollin)
>             ^~~~~~~~~~~
> fs/io_uring.c:4182:2: note: uninitialized use occurs here
>         mask |= POLLERR | POLLPRI;
>         ^~~~
> fs/io_uring.c:4178:2: note: remove the 'if' if its condition is always
> true
>         if (def->pollin)
>         ^~~~~~~~~~~~~~~~
> fs/io_uring.c:4154:15: note: initialize the variable 'mask' to silence
> this warning
>         __poll_t mask, ret;
>                      ^
>                       = 0
> 1 warning generated.
> 
> io_op_defs has many definitions where pollin is not set so mask indeed
> might be uninitialized. Initialize it to zero and change the next
> assignment to |=, in case further masks are added in the future to avoid
> missing changing the assignment then.
> 
> Fixes: d7718a9d25a6 ("io_uring: use poll driven retry for files that support it")
> Link: https://github.com/ClangBuiltLinux/linux/issues/916
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
> 
> I noticed that for-next has been force pushed; if you want to squash
> this into the commit that it fixes (or fix it in a different way), feel
> free.

Great thanks, applied. I wonder why gcc doesn't warn about that...

-- 
Jens Axboe