[PATCH 2/3] f2fs crypto: add missing locking for keyring_key access

[Eric Biggers <ebiggers3@gmail.com>]

From: Jaegeuk Kim <jaegeuk@kernel.org>

commit 745e8490b1e960ad79859dd8ba6a0b5a8d3d994e upstream.  Please apply
to 4.4-stable.

This patch adopts:
	ext4 crypto: add missing locking for keyring_key access

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/f2fs/crypto_key.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/f2fs/crypto_key.c b/fs/f2fs/crypto_key.c
index 81c87f7a3251..ae49be377b60 100644
--- a/fs/f2fs/crypto_key.c
+++ b/fs/f2fs/crypto_key.c
@@ -193,9 +193,11 @@ int f2fs_get_encryption_info(struct inode *inode)
 		res = -ENOKEY;
 		goto out;
 	}
+	down_read(&keyring_key->sem);
 	ukp = user_key_payload(keyring_key);
 	if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 		res = -EINVAL;
+		up_read(&keyring_key->sem);
 		goto out;
 	}
 	master_key = (struct f2fs_encryption_key *)ukp->data;
@@ -206,10 +208,12 @@ int f2fs_get_encryption_info(struct inode *inode)
 				"f2fs: key size incorrect: %d\n",
 				master_key->size);
 		res = -ENOKEY;
+		up_read(&keyring_key->sem);
 		goto out;
 	}
 	res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
 				  raw_key);
+	up_read(&keyring_key->sem);
 	if (res)
 		goto out;
 
-- 
2.15.0.rc0.271.g36b669edcc-goog