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Message-ID: <125071.1690359924@warthog.procyon.org.uk>
Date: Wed, 26 Jul 2023 09:25:24 +0100
From: David Howells <dhowells@...hat.com>
To: Sven Schnelle <svens@...ux.ibm.com>
Cc: dhowells@...hat.com,
syzbot <syzbot+9b82859567f2e50c123e@...kaller.appspotmail.com>,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, syzkaller-bugs@...glegroups.com,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S. Miller" <davem@...emloft.net>,
linux-crypto@...r.kernel.org
Subject: Re: [syzbot] [mm?] WARNING in try_grab_page
Sven Schnelle <svens@...ux.ibm.com> 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
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