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crypto: af_alg: Pin pages rather than ref'ing if appropriate

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Convert AF_ALG to use iov_iter_extract_pages() instead of
iov_iter_get_pages().  This will pin pages or leave them unaltered rather
than getting a ref on them as appropriate to the iterator.

The pages need to be pinned for DIO-read rather than having refs taken on
them to prevent VM copy-on-write from malfunctioning during a concurrent
fork() (the result of the I/O would otherwise end up only visible to the
child process and not the parent).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-crypto@vger.kernel.org
cc: netdev@vger.kernel.org
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
David Howells 2023-06-06 14:08:51 +01:00 committed by Paolo Abeni
parent f5f82cd187
commit f9e7a5fa51
2 changed files with 8 additions and 3 deletions
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10
crypto/af_alg.c
View file

@ -533,14 +533,17 @@ static const struct net_proto_family alg_family = {
int af_alg_make_sg(struct af_alg_sgl *sgl, struct iov_iter *iter, int len)
{
struct page **pages = sgl->pages;
size_t off;
ssize_t n;
int npages, i;
n = iov_iter_get_pages2(iter, sgl->pages, len, ALG_MAX_PAGES, &off);
n = iov_iter_extract_pages(iter, &pages, len, ALG_MAX_PAGES, 0, &off);
if (n < 0)
return n;
sgl->need_unpin = iov_iter_extract_will_pin(iter);
npages = DIV_ROUND_UP(off + n, PAGE_SIZE);
if (WARN_ON(npages == 0))
return -EINVAL;
@ -573,8 +576,9 @@ void af_alg_free_sg(struct af_alg_sgl *sgl)
{
int i;
for (i = 0; i < sgl->npages; i++)
put_page(sgl->pages[i]);
if (sgl->need_unpin)
for (i = 0; i < sgl->npages; i++)
unpin_user_page(sgl->pages[i]);
}
EXPORT_SYMBOL_GPL(af_alg_free_sg);

1
include/crypto/if_alg.h
View file

@ -59,6 +59,7 @@ struct af_alg_sgl {
struct scatterlist sg[ALG_MAX_PAGES + 1];
struct page *pages[ALG_MAX_PAGES];
unsigned int npages;
bool need_unpin;
};
/* TX SGL entry */