Merge tag 'keys-fixes-20200329' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull keyrings fixes from David Howells:
 "Here's a couple of patches that fix a circular dependency between
  holding key->sem and mm->mmap_sem when reading data from a key.

  One potential issue is that a filesystem looking to use a key inside,
  say, ->readpages() could deadlock if the key being read is the key
  that's required and the buffer the key is being read into is on a page
  that needs to be fetched.

  The case actually detected is a bit more involved - with a filesystem
  calling request_key() and locking the target keyring for write - which
  could be being read"

* tag 'keys-fixes-20200329' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  KEYS: Avoid false positive ENOMEM error on key read
  KEYS: Don't write out to userspace while holding key semaphore

1 files changed, 2 insertions, 12 deletions

diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index d2c5ec1e040b..8001ab07e63b 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -1130,11 +1130,10 @@ out:
  * trusted_read - copy the sealed blob data to userspace in hex.
  * On success, return to userspace the trusted key datablob size.
  */
-static long trusted_read(const struct key *key, char __user *buffer,
+static long trusted_read(const struct key *key, char *buffer,
 			 size_t buflen)
 {
 	const struct trusted_key_payload *p;
-	char *ascii_buf;
 	char *bufp;
 	int i;
 
@@ -1143,18 +1142,9 @@ static long trusted_read(const struct key *key, char __user *buffer,
 		return -EINVAL;
 
 	if (buffer && buflen >= 2 * p->blob_len) {
-		ascii_buf = kmalloc_array(2, p->blob_len, GFP_KERNEL);
-		if (!ascii_buf)
-			return -ENOMEM;
-
-		bufp = ascii_buf;
+		bufp = buffer;
 		for (i = 0; i < p->blob_len; i++)
 			bufp = hex_byte_pack(bufp, p->blob[i]);
-		if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) {
-			kzfree(ascii_buf);
-			return -EFAULT;
-		}
-		kzfree(ascii_buf);
 	}
 	return 2 * p->blob_len;
 }