linux-kernel - Re: [PATCH] fs/ceph/file: fix memory leaks in __ceph_sync

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Message-ID: <CAKPOu+9H+NGa44_p4DDw3H=kWfi-zANN_wb3OtsQScjDGmecyQ@mail.gmail.com>
Date: Thu, 28 Nov 2024 13:31:24 +0100
From: Max Kellermann <max.kellermann@...os.com>
To: Alex Markuze <amarkuze@...hat.com>
Cc: xiubli@...hat.com, idryomov@...il.com, ceph-devel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] fs/ceph/file: fix memory leaks in __ceph_sync_read()

On Thu, Nov 28, 2024 at 1:28 PM Max Kellermann <max.kellermann@...os.com> wrote:
>
> On Thu, Nov 28, 2024 at 1:18 PM Alex Markuze <amarkuze@...hat.com> wrote:
> > Pages are freed in `ceph_osdc_put_request`, trying to release them
> > this way will end badly.
>
> I don't get it. If this ends badly, why does the other
> ceph_release_page_vector() call after ceph_osdc_put_request() in that
> function not end badly?

Look at this piece:

        osd_req_op_extent_osd_data_pages(req, 0, pages, read_len,
                         offset_in_page(read_off),
                         false, false);

The last parameter is "own_pages". Ownership of these pages is NOT
transferred to the osdc request, therefore ceph_osdc_put_request()
will NOT free them, and this is really a leak bug and my patch fixes
it.

I just saw this piece of code for the first time, I have no idea. What
am I missing?