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Groups > linux.kernel > #1661302

[PATCH 02/23] security: use READ_ONCE instead of deprecated ACCESS_ONCE

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From: Davidlohr Bueso <dave@stgolabs.net>

With the new standardized functions, we can replace all ACCESS_ONCE()
calls across relevant security/keyrings/.

ACCESS_ONCE() does not work reliably on non-scalar types. For example
gcc 4.6 and 4.7 might remove the volatile tag for such accesses during
the SRA (scalar replacement of aggregates) step:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

Update the new calls regardless of if it is a scalar type, this is
cleaner than having three alternatives.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 security/keys/keyring.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 4d1678e4586f..de81793f9920 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -706,7 +706,7 @@ static bool search_nested_keyrings(struct key *keyring,
 	 * Non-keyrings avoid the leftmost branch of the root entirely (root
 	 * slots 1-15).
 	 */
-	ptr = ACCESS_ONCE(keyring->keys.root);
+	ptr = READ_ONCE(keyring->keys.root);
 	if (!ptr)
 		goto not_this_keyring;
 
@@ -720,7 +720,7 @@ static bool search_nested_keyrings(struct key *keyring,
 		if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
 			goto not_this_keyring;
 
-		ptr = ACCESS_ONCE(shortcut->next_node);
+		ptr = READ_ONCE(shortcut->next_node);
 		node = assoc_array_ptr_to_node(ptr);
 		goto begin_node;
 	}
@@ -740,7 +740,7 @@ static bool search_nested_keyrings(struct key *keyring,
 	if (assoc_array_ptr_is_shortcut(ptr)) {
 		shortcut = assoc_array_ptr_to_shortcut(ptr);
 		smp_read_barrier_depends();
-		ptr = ACCESS_ONCE(shortcut->next_node);
+		ptr = READ_ONCE(shortcut->next_node);
 		BUG_ON(!assoc_array_ptr_is_node(ptr));
 	}
 	node = assoc_array_ptr_to_node(ptr);
@@ -752,7 +752,7 @@ static bool search_nested_keyrings(struct key *keyring,
 ascend_to_node:
 	/* Go through the slots in a node */
 	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
-		ptr = ACCESS_ONCE(node->slots[slot]);
+		ptr = READ_ONCE(node->slots[slot]);
 
 		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
 			goto descend_to_node;
@@ -790,13 +790,13 @@ static bool search_nested_keyrings(struct key *keyring,
 	/* We've dealt with all the slots in the current node, so now we need
 	 * to ascend to the parent and continue processing there.
 	 */
-	ptr = ACCESS_ONCE(node->back_pointer);
+	ptr = READ_ONCE(node->back_pointer);
 	slot = node->parent_slot;
 
 	if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
 		shortcut = assoc_array_ptr_to_shortcut(ptr);
 		smp_read_barrier_depends();
-		ptr = ACCESS_ONCE(shortcut->back_pointer);
+		ptr = READ_ONCE(shortcut->back_pointer);
 		slot = shortcut->parent_slot;
 	}
 	if (!ptr)

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[PATCH 00/23] KEYS: Fixes David Howells <dhowells@redhat.com> - 2017-06-08 15:50 +0200
  [PATCH 05/23] KEYS: Delete an error message for a failed memory  allocation in get_derived_key() David Howells <dhowells@redhat.com> - 2017-06-08 15:50 +0200
  [PATCH 18/23] KEYS: DH: forbid using digest_null as the KDF hash David Howells <dhowells@redhat.com> - 2017-06-08 15:50 +0200
  [PATCH 10/23] KEYS: encrypted: use constant-time HMAC comparison David Howells <dhowells@redhat.com> - 2017-06-08 15:50 +0200
  [PATCH 04/23] X.509: Fix error code in x509_cert_parse() David Howells <dhowells@redhat.com> - 2017-06-08 15:50 +0200
  [PATCH 07/23] KEYS: encrypted: avoid encrypting/decrypting stack  buffers David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 20/23] KEYS: DH: ensure the KDF counter is properly aligned David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 19/23] KEYS: DH: don't feed uninitialized "otherinfo" into  KDF David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 16/23] KEYS: trusted: sanitize all key material David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 21/23] KEYS: DH: add __user annotations to keyctl_kdf_params David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 13/23] KEYS: sanitize add_key() and keyctl() key payloads David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 14/23] KEYS: user_defined: sanitize key payloads David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 22/23] crypto : asymmetric_keys : verify_pefile:zero memory  content before freeing David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 23/23] KEYS: Convert KEYCTL_DH_COMPUTE to use the crypto KPP  API David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 11/23] KEYS: fix dereferencing NULL payload with nonzero  length David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 09/23] KEYS: encrypted: fix race causing incorrect HMAC  calculations David Howells <dhowells@redhat.com> - 2017-06-08 16:00 +0200
  [PATCH 08/23] KEYS: encrypted: fix buffer overread in  valid_master_desc() David Howells <dhowells@redhat.com> - 2017-06-08 16:10 +0200
  [PATCH 02/23] security: use READ_ONCE instead of deprecated  ACCESS_ONCE David Howells <dhowells@redhat.com> - 2017-06-08 16:10 +0200
  Re: [PATCH 00/23] KEYS: Fixes James Morris <jmorris@namei.org> - 2017-06-08 16:40 +0200
    Re: [PATCH 00/23] KEYS: Fixes David Howells <dhowells@redhat.com> - 2017-06-08 16:50 +0200

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