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

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Message-ID: <2af2d61f-bd3d-5288-7bd2-4768ebe266d7@bytedance.com>
Date:   Tue, 8 Feb 2022 13:37:22 +0000
From:   Usama Arif <usama.arif@...edance.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>, trix@...hat.com,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [External] [PATCH] io_uring: Fix use of uninitialized ret in
 io_eventfd_register()



On 07/02/2022 16:24, Nathan Chancellor 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")
> 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(-)
>

Thanks for pointing this out. Just for some background in earlier 
revisions of the patch for "io_uring: avoid ring quiesce while 
registering/unregistering eventfd" the error return part was being 
handled differently, but ended up looking similar to before in the final 
revision that got merged, but i forgot to change this part back. Would 
it be possible to fold the below diff into the patch as well Jens?
Thanks and sorry for missing this!

Regards,
Usama

> 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
>