linux-kernel - Re: [PATCH] io_uring: Fix use of uninitialized ret in io_eventfd

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Message-ID: <CAKwvOdnfQeY8sC0iET4hm-kgeFhurWf_jrh4=czBj17zQ5+x0Q@mail.gmail.com>
Date:   Mon, 7 Feb 2022 11:32:03 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        Usama Arif <usama.arif@...edance.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] io_uring: Fix use of uninitialized ret in io_eventfd_register()

On Mon, Feb 7, 2022 at 8:24 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> Clang warns:
>
>   fs/io_uring.c:9396:9: warning: variable 'ret' is uninitialized when used here [-Wuninitialized]
>           return ret;
>                  ^~~
>   fs/io_uring.c:9373:13: note: initialize the variable 'ret' to silence this warning
>           int fd, ret;
>                      ^
>                       = 0
>   1 warning generated.
>
> Just return 0 directly and reduce the scope of ret to the if statement,
> as that is the only place that it is used, which is how the function was
> before the fixes commit.
>
> Fixes: 1a75fac9a0f9 ("io_uring: avoid ring quiesce while registering/unregistering eventfd")

Did SHA's change? In linux-next, I see:
commit b77e315a9644 ("io_uring: avoid ring quiesce while
registering/unregistering eventfd")
otherwise LGTM

> Link: https://github.com/ClangBuiltLinux/linux/issues/1579
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  fs/io_uring.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 5479f0607430..7ef04bb66da1 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -9370,7 +9370,7 @@ static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
>  {
>         struct io_ev_fd *ev_fd;
>         __s32 __user *fds = arg;
> -       int fd, ret;
> +       int fd;
>
>         ev_fd = rcu_dereference_protected(ctx->io_ev_fd,
>                                         lockdep_is_held(&ctx->uring_lock));
> @@ -9386,14 +9386,14 @@ static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
>
>         ev_fd->cq_ev_fd = eventfd_ctx_fdget(fd);
>         if (IS_ERR(ev_fd->cq_ev_fd)) {
> -               ret = PTR_ERR(ev_fd->cq_ev_fd);
> +               int ret = PTR_ERR(ev_fd->cq_ev_fd);
>                 kfree(ev_fd);
>                 return ret;
>         }
>         ev_fd->eventfd_async = eventfd_async;
>
>         rcu_assign_pointer(ctx->io_ev_fd, ev_fd);
> -       return ret;
> +       return 0;
>  }
>
>  static void io_eventfd_put(struct rcu_head *rcu)
>
> base-commit: 88a0394bc27de2dd8a8715970f289c5627052532
> --
> 2.35.1
>
>


-- 
Thanks,
~Nick Desaulniers