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: 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>
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@ -533,14 +533,17 @@ static const struct net_proto_family alg_family = {
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int af_alg_make_sg(struct af_alg_sgl *sgl, struct iov_iter *iter, int len)
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{
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struct page **pages = sgl->pages;
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size_t off;
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ssize_t n;
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int npages, i;
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n = iov_iter_get_pages2(iter, sgl->pages, len, ALG_MAX_PAGES, &off);
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n = iov_iter_extract_pages(iter, &pages, len, ALG_MAX_PAGES, 0, &off);
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if (n < 0)
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return n;
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sgl->need_unpin = iov_iter_extract_will_pin(iter);
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npages = DIV_ROUND_UP(off + n, PAGE_SIZE);
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if (WARN_ON(npages == 0))
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return -EINVAL;
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@ -573,8 +576,9 @@ void af_alg_free_sg(struct af_alg_sgl *sgl)
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{
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int i;
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for (i = 0; i < sgl->npages; i++)
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put_page(sgl->pages[i]);
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if (sgl->need_unpin)
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for (i = 0; i < sgl->npages; i++)
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unpin_user_page(sgl->pages[i]);
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}
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EXPORT_SYMBOL_GPL(af_alg_free_sg);
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@ -59,6 +59,7 @@ struct af_alg_sgl {
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struct scatterlist sg[ALG_MAX_PAGES + 1];
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struct page *pages[ALG_MAX_PAGES];
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unsigned int npages;
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bool need_unpin;
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};
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/* TX SGL entry */
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