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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <000000000000273d0105ff97bf56@google.com> To: Sven Schnelle Cc: dhowells@redhat.com, syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Herbert Xu , "David S. Miller" , linux-crypto@vger.kernel.org Subject: Re: [syzbot] [mm?] WARNING in try_grab_page MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <35255.1690277311.1@warthog.procyon.org.uk> Date: Tue, 25 Jul 2023 10:28:31 +0100 Message-ID: <35256.1690277311@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Rspamd-Queue-Id: 04684140015 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: jbwjyj6whc9i3eco81eu3npyqyjh5jgd X-HE-Tag: 1690277319-999106 X-HE-Meta: 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 5W7CiS6d /agnsp0+7+ze3eRcR8wHR+MqUyxTg71WlRjI3yaG4uVVvQyHxStLxyMbWjiY9Lfbj3kshTlhZNVtLLYsGGUBQD8vX1oZ5AFiweC65xkqQpUGSf24i921UOVDhIhNGISJL5pasueso6io31GE1mOJMjEKH8g6DwbZQTWb3kV1EhmQYY3bZauFwZDYAlNfC1Mt4mU6OSPSd7u+i+mJRZuNduB7bdWVigxK4iByB+aUfwLQ8ZEq/o7QnRMaAbI8ovLlDmh8W6EJceRxh2n0g4l1AqbmECbnsTTHTnWOgQyJNh+5xi1Rr0xO74Z712oSv3SQQdlEM+3/NPRF2YHkMa3kBFULmBPhSX3xHhc+2+4/GxBjiSC4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Sven Schnelle wrote: > > I looked into this issue. What syzkaller is doing is opening an AF_ALG > socket, and sending a large message which will eventually end in -EFAULT. > Looking at the code in crypto/algif_hash.c i see that hash_sendmsg is > calling extract_iter_to_sg() -> extract_user_to_sg(). In the -EFAULT > case, this function is calling put_page(), which looks like a leftover > from the old pinning interface. I think this should be a > unpin_user_page() call now. > > However, hash_sendmsg() also unpins via af_alg_free_sg() in the error > path. From an API perspective, i would prefer if extract_user_to_sg() > does the unpinning on error. Any thoughts? Good catch, thanks. I'll whip up a patch or two for it. David