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authorArd Biesheuvel <ardb@kernel.org>2022-12-13 19:13:10 +0300
committerHerbert Xu <herbert@gondor.apana.org.au>2022-12-30 17:56:27 +0300
commitaa9695157f65c55e5c85a1c194859d3c03e68018 (patch)
tree92cab03ac269b23b3211b3d5ae41317c389fa536 /crypto/shash.c
parentb517b0fbfec836391427649b207735afb698fcf3 (diff)
downloadlinux-aa9695157f65c55e5c85a1c194859d3c03e68018.tar.xz
crypto: scatterwalk - use kmap_local() not kmap_atomic()
kmap_atomic() is used to create short-lived mappings of pages that may not be accessible via the kernel direct map. This is only needed on 32-bit architectures that implement CONFIG_HIGHMEM, but it can be used on 64-bit other architectures too, where the returned mapping is simply the kernel direct address of the page. However, kmap_atomic() does not support migration on CONFIG_HIGHMEM configurations, due to the use of per-CPU kmap slots, and so it disables preemption on all architectures, not just the 32-bit ones. This implies that all scatterwalk based crypto routines essentially execute with preemption disabled all the time, which is less than ideal. So let's switch scatterwalk_map/_unmap and the shash/ahash routines to kmap_local() instead, which serves a similar purpose, but without the resulting impact on preemption on architectures that have no need for CONFIG_HIGHMEM. Cc: Eric Biggers <ebiggers@kernel.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "Elliott, Robert (Servers)" <elliott@hpe.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/shash.c')
-rw-r--r--crypto/shash.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/crypto/shash.c b/crypto/shash.c
index 868b6ba2b3b7..58b46f198449 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -320,10 +320,10 @@ int shash_ahash_digest(struct ahash_request *req, struct shash_desc *desc)
nbytes <= min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset))) {
void *data;
- data = kmap_atomic(sg_page(sg));
+ data = kmap_local_page(sg_page(sg));
err = crypto_shash_digest(desc, data + offset, nbytes,
req->result);
- kunmap_atomic(data);
+ kunmap_local(data);
} else
err = crypto_shash_init(desc) ?:
shash_ahash_finup(req, desc);