From: Eric Biggers <ebiggers@xxxxxxxxxx>
commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream. Please apply
to 4.4-stable.
When an fscrypt-encrypted file is opened, we request the file's master
key from the keyrings service as a logon key, then access its payload.
However, a revoked key has a NULL payload, and we failed to check for
this. request_key() *does* skip revoked keys, but there is still a
window where the key can be revoked before we acquire its semaphore.
Fix it by checking for a NULL payload, treating it like a key which was
already revoked at the time it was requested.
Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
Reviewed-by: James Morris <james.l.morris@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [v4.1+]
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/ext4/crypto_key.c | 6 ++++++
fs/f2fs/crypto_key.c | 6 ++++++
2 files changed, 12 insertions(+)
diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c
index 505f8afde57c..9a1bc638abce 100644
--- a/fs/ext4/crypto_key.c
+++ b/fs/ext4/crypto_key.c
@@ -204,6 +204,12 @@ int ext4_get_encryption_info(struct inode *inode)
}
down_read(&keyring_key->sem);
ukp = user_key_payload(keyring_key);
+ if (!ukp) {
+ /* key was revoked before we acquired its semaphore */
+ res = -EKEYREVOKED;
+ up_read(&keyring_key->sem);
+ goto out;
+ }
if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
res = -EINVAL;
up_read(&keyring_key->sem);
diff --git a/fs/f2fs/crypto_key.c b/fs/f2fs/crypto_key.c
index ae49be377b60..7e62889a1d3d 100644
--- a/fs/f2fs/crypto_key.c
+++ b/fs/f2fs/crypto_key.c
@@ -195,6 +195,12 @@ int f2fs_get_encryption_info(struct inode *inode)
}
down_read(&keyring_key->sem);
ukp = user_key_payload(keyring_key);
+ if (!ukp) {
+ /* key was revoked before we acquired its semaphore */
+ res = -EKEYREVOKED;
+ up_read(&keyring_key->sem);
+ goto out;
+ }
if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
res = -EINVAL;
up_read(&keyring_key->sem);
--
2.15.0.rc0.271.g36b669edcc-goog