linux-kernel - Re: [PATCH] io_uring/rsrc: remove unnecessary check on resv2

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Message-ID: <CADPKJ-78+=j_HkUcJt2k6Xsn-fjs8=xT97j+coWNAEzTFvHr6g@mail.gmail.com>
Date: Tue, 23 Sep 2025 17:10:38 +0800
From: clingfei <clf700383@...il.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring/rsrc: remove unnecessary check on resv2

Jens Axboe <axboe@...nel.dk> 于2025年9月23日周二 16:50写道：
>
> On 9/23/25 2:41 AM, clingfei wrote:
> > From b52509776e0f7f9ea703d0551ccaeeaa49ab6440 Mon Sep 17 00:00:00 2001
> > From: clingfei <clf700383@...il.com>
> > Date: Tue, 23 Sep 2025 16:30:30 +0800
> > Subject: [PATCH] io_uring/rsrc: remove unnecessary check on resv2
> >
> > The memset sets the up.resv2 to be 0,
> > and the copy_from_user does not touch it,
> > thus up.resv2 will always be false.
>
> Please wrap commit messages at around ~72 chars.
>
> > Signed-off-by: clingfei <clf700383@...il.com>
> > ---
> >  io_uring/rsrc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> > index f75f5e43fa4a..7006b3ca5404 100644
> > --- a/io_uring/rsrc.c
> > +++ b/io_uring/rsrc.c
> > @@ -372,7 +372,7 @@ int io_register_files_update(struct io_ring_ctx
> > *ctx, void __user *arg,
> >     memset(&up, 0, sizeof(up));
> >     if (copy_from_user(&up, arg, sizeof(struct io_uring_rsrc_update)))
> >         return -EFAULT;
> > -   if (up.resv || up.resv2)
> > +   if (up.resv)
> >         return -EINVAL;
> >     return __io_register_rsrc_update(ctx, IORING_RSRC_FILE, &up, nr_args);
> >  }
>
> White space damaged patch, but more importantly, I don't think this is
> worth adding. Yes it'll never overwrite resv2 because of the different
> sizes. Curious how you ran into this?
>
> --
> Jens Axboe

During my review of the io_uring code, I noticed that
sizeof(io_uring_rsrc_update) is used to initialize a struct
io_uring_rsrc_update2. My initial suspicion was that this might be an
error, but upon closer inspection, I verified that this usage is
intentional and correct.