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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: <125070.1690359924.1@warthog.procyon.org.uk> Date: Wed, 26 Jul 2023 09:25:24 +0100 Message-ID: <125071.1690359924@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Rspamd-Queue-Id: 63FE24001E X-Rspam-User: X-Stat-Signature: 3ikqfsy5htyzeam359gasqxc5s9c6jd4 X-Rspamd-Server: rspam01 X-HE-Tag: 1690359932-76284 X-HE-Meta: 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 LcYECqt3 Hm4mN64/YqgEfvgdchv9iwsd7F7/Sne66KoY4YLqand8WmpItwHWtnVznqOUTMDwv9IvzzEqwg+IIaMTGieikhKu/HOwRxk4NMRb72LmG6lkJYmxIrLnGsSyeYfC2WKyK92qFw/ybhnC8jWMGevWCoKY3yPu7NwVHK34XHzxJh1F+znIFCSjY8/dTnPVTGFIkEapRMGnLZxR8X/jaxX1sbopEJCbgTLs4dat+4pQnjt4tP3PdGWcTjoYWU1uBVPyvEURi59eDQSqVnvL3KY0ZrfLDcZfrTZLSEjj5mM06H7fZeNBvbGYMNG9EcEU+AgXC9hPnrwRN7yc0qj8XiC5Qfnhy8y6Xh+l4jSjcHMAPeF58IDJ8e3fjezwnKURuByYwg+V3Rr1Aaz6a01N8Yb0Q8T0EQurFA52UXdsh 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: > 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? In the event of an error, extract_user_to_sg() unpins only the pages it added to the scatterlist; it doesn't unpin any pages that were already there and doesn't free the scatterlist; it also decrements sgtable->nents so that the caller doesn't see the pages it attempted to add, so calling af_alg_free_sg() shouldn't hurt. Note that the error path also frees the result, so we do need to do at least part of it. David