From: Eric Biggers Date: Mon, 9 Oct 2017 19:46:18 +0000 (-0700) Subject: fscrypt: fix dereference of NULL user_key_payload X-Git-Tag: v4.4.95~4 X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1dda04c761abf006402f7f5e9adb11f9044731c8;p=linux fscrypt: fix dereference of NULL user_key_payload commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream. 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 Cc: [v4.1+] Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: Greg Kroah-Hartman --- 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sem); ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + up_read(&keyring_key-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sem); ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + up_read(&keyring_key-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);