From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 110222E4241; Mon, 16 Jun 2025 12:09:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750075770; cv=none; b=AkJEhxHAIEuKQGgDCsFp+bznV8mjaZ4ojUGe8DZcb2U4F6fdMZPp6HVJlFkTZLzgj9qQ6JCsAvHtKIQES/i5TyNa+spMv1A2cMNhsdlYLZK+7KWT1DC2OTa1z2LZZtLXsX6vyBhGgD93lYid5kOV1nsmBIL/b6P45lY/fmDWswc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750075770; c=relaxed/simple; bh=Wo2XxdbZ7pdAohMk152uhjRRyVn8l8Io4GmZZilbNg8=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ZX6ewZ/VlMoE4VsXBmgNof8g+OYxrxjpFUUbYX7OtGHvT9bQzLR28emU+akI5sm+3jnpL9n/rxvo0hTgxpCI2QRaV6fCDRonRiN4MVnpxdoT+vPWS+pKj4EAhmJVm4LxZF/ptIVVM0+tdN6Uc847SzxG3J5GCs2tanqh7t1dgns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YwIgOHM4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YwIgOHM4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D40A9C4CEEA; Mon, 16 Jun 2025 12:09:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750075769; bh=Wo2XxdbZ7pdAohMk152uhjRRyVn8l8Io4GmZZilbNg8=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=YwIgOHM4Kt/F0zhoo6+5uwnZACjGD4TRomb6eOMF907AG/xRYvSi+oqRdBg4F5B23 +oD+7BWzSdJNj+vaYrlzLQB53XocGOIS+FkR5IYp7Ll/wPhKkJXZkDRhDzYXnnxtdB bSpXknJA8bzcWrAOXGRu7RoufTFhoUSoxuKX1AtWNS1iT22EFGSFAHbYho+Fuhm9mC yWA2SxHKn12h4cx/iul35IAHN/oh7+AjeGnCDQIsvdHQX/FF4YUtlQ8GqjRIXEE2f0 aiDdkN+0mIhiOjWJl2ofR4M2n0+bOR6k+sH4Iy8zni7Nz1rJg2Eg6ODQc4FeG6rBIo wT4Cf93DTzmsg== Message-ID: <219985d542d0eb765d917c0ab620b6af5c62f1af.camel@kernel.org> Subject: Re: [PATCH v2 1/5] nfsd: prevent callback tasks running concurrently From: Jeff Layton To: ChenXiaoSong Cc: Olga Kornievskaia , Li Lingfeng , Dai Ngo , Neil Brown , Chuck Lever , Tom Talpey , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 16 Jun 2025 08:09:27 -0400 In-Reply-To: <6E9B7F9B8D47F98B+d6fd7e8f-de81-4ec3-b3ae-f85bbb744e66@chenxiaosong.com> References: <20250220-nfsd-callback-v2-0-6a57f46e1c3a@kernel.org> <20250220-nfsd-callback-v2-1-6a57f46e1c3a@kernel.org> <23651194C61FBB9C+e2ddd3f5-f51f-44c0-8800-d2abb08a2447@chenxiaosong.com> <208bd615061231c035a5633b29190925f271bd4b.camel@kernel.org> <64E3DD4D765DEAD1+87aeb2d4-3732-4e57-ada6-098dbf0a7feb@chenxiaosong.com> 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f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-06-16 at 15:49 +0800, ChenXiaoSong wrote: > Hi Jeff: >=20 > Do you have any suggestions for this null-ptr-deref issue? >=20 > Here is the link to the vmcore analysis: >=20 > https://chenxiaosong.com/en/nfs/en-null-ptr-deref-in-nfsd4_probe_callback= .html >=20 > Thanks, > ChenXiaoSong. >=20 Not right offhand. My first guess would be some sort of UAF. Maybe a nfs4_client refcounting issue? If this is reproducible then you may want to turn up KASAN which might give you more info. That said, 4.19.90 is more than 6 years old at this point. You may want to consider moving to something more recent. > =E5=9C=A8 2025/6/11 15:12, ChenXiaoSong =E5=86=99=E9=81=93: > > =E5=9C=A8 2025/6/10 19:09, Jeff Layton =E5=86=99=E9=81=93: > > >=20 > > > Synchronization was probably too strong a word. I remember looking ov= er > > > this code and convincing myself that the probe callback wasn't subjec= t > > > to the same races as the others, but I think that was mostly because > > > the outcome of those races was not harmful. Note that the probe itsel= f > > > can actually be run at the start of a completely unrelated callback t= o > > > the same client. > > >=20 > > > So you hit a NULL pointer in __queue_work()? The work_struct is > > > embedded in the nfs4_client so that would probably imply that that th= e > > > nfs4_client struct was corrupt? > > >=20 > > > You may want to get a vmcore and analyze it if you can reproduce this= . > >=20 > > Thanks for your reply. > >=20 > > I have already got a vmcore. Here is the link to the vmcore analysis: > >=20 > > https://chenxiaosong.com/en/nfs/en-null-ptr-deref-in-=20 > > nfsd4_probe_callback.html > >=20 > > Please let me know if you need any more detailed information. > >=20 > > Thanks, > > ChenXiaoSong. >=20 --=20 Jeff Layton