Commit f9e7a5fa authored by David Howells's avatar David Howells Committed by Paolo Abeni
Browse files

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



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: default avatarDavid 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: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent f5f82cd1

crypto/af_alg.c

+7 −3
Original line number Diff line number Diff line
@@ -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;



	if (sgl->need_unpin)

		for (i = 0; i < sgl->npages; i++)

		put_page(sgl->pages[i]);

			unpin_user_page(sgl->pages[i]);

}

EXPORT_SYMBOL_GPL(af_alg_free_sg);

include/crypto/if_alg.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */