[RFC PATCH v2 21/48] crypto: af_alg: Pin pages rather than ref'ing if appropriate
From: David Howells <dhowells@redhat.com>
Date: 2023-03-29 14:18:12
Also in:
linux-crypto, linux-fsdevel, linux-mm, lkml
Subsystem:
crypto api, the rest · Maintainers:
Herbert Xu, "David S. Miller", Linus Torvalds
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: linux-crypto@vger.kernel.org --- crypto/af_alg.c | 10 +++++++--- include/crypto/if_alg.h | 1 + 2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 5f7252a5b7b4..7caff10df643 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c@@ -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);
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index 7e76623f9ec3..46494b33f5bc 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h@@ -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 */