linux-kernel - Re: [PATCH] md/bitmap: fix GPF in write

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Message-ID: <CAMGffEmMO59xc2DOVo2A4dat7Vm7N6E+tHH2ZM0GpVCD796mtw@mail.gmail.com>
Date: Mon, 26 Jan 2026 09:21:12 +0100
From: Jinpu Wang <jinpu.wang@...os.com>
To: yukuai@...as.com
Cc: song@...nel.org, linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH] md/bitmap: fix GPF in write_page caused by resize race

On Mon, Jan 26, 2026 at 6:33 AM Yu Kuai <yukuai@...as.com> wrote:
>
> 在 2026/1/20 18:24, Jack Wang 写道:
>
> > A General Protection Fault occurs in write_page() during array resize:
> > RIP: 0010:write_page+0x22b/0x3c0 [md_mod]
> >
> > This is a use-after-free race between bitmap_daemon_work() and
> > __bitmap_resize(). The daemon iterates over `bitmap->storage.filemap`
> > without locking, while the resize path frees that storage via
> > md_bitmap_file_unmap(). `quiesce()` does not stop the md thread,
> > allowing concurrent access to freed pages.
> >
> > Fix by holding `mddev->bitmap_info.mutex` during the bitmap update.
> >
> > Closes:https://lore.kernel.org/linux-raid/CAMGffE=Mbfp=7xD_hYxXk1PAaCZNSEAVeQGKGy7YF9f2S4=NEA@mail.gmail.com/T/#u
> > Cc:stable@...r.kernel.org
> > Signed-off-by: Jack Wang<jinpu.wang@...os.com>
> > ---
> >   drivers/md/md-bitmap.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
>
> Applied with a fixtag:
>
> Fixes: d60b479d177a ("md/bitmap: add bitmap_resize function to allow
> bitmap resizing.")
>
> --
> Thansk,
> Kuai
Hi Kuai,

Thanks for applying the fix with the fixes tag.

Best,
Jinpu