diff options
| author | Eric Biggers <ebiggers@google.com> | 2016-11-13 20:41:09 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2016-11-19 20:56:13 -0500 |
| commit | 0f0909e242f73c1154272cf04f07fc9afe13e5b8 (patch) | |
| tree | ff64e7ce77a05f3cfebe72b2f2706bf5f2101e88 | |
| parent | 3c7018ebf8dbf14e7cd4f5dc648c51fc979f45bb (diff) | |
fscrypto: don't use on-stack buffer for key derivation
With the new (in 4.9) option to use a virtually-mapped stack
(CONFIG_VMAP_STACK), stack buffers cannot be used as input/output for
the scatterlist crypto API because they may not be directly mappable to
struct page. get_crypt_info() was using a stack buffer to hold the
output from the encryption operation used to derive the per-file key.
Fix it by using a heap buffer.
This bug could most easily be observed in a CONFIG_DEBUG_SG kernel
because this allowed the BUG in sg_set_buf() to be triggered.
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/crypto/keyinfo.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 82f0285f5d08..67fb6d8876d0 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -185,7 +185,7 @@ int get_crypt_info(struct inode *inode) struct crypto_skcipher *ctfm; const char *cipher_str; int keysize; - u8 raw_key[FS_MAX_KEY_SIZE]; + u8 *raw_key = NULL; int res; res = fscrypt_initialize(); @@ -238,6 +238,15 @@ retry: if (res) goto out; + /* + * This cannot be a stack buffer because it is passed to the scatterlist + * crypto API as part of key derivation. + */ + res = -ENOMEM; + raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS); + if (!raw_key) + goto out; + if (fscrypt_dummy_context_enabled(inode)) { memset(raw_key, 0x42, FS_AES_256_XTS_KEY_SIZE); goto got_key; @@ -276,7 +285,8 @@ got_key: if (res) goto out; - memzero_explicit(raw_key, sizeof(raw_key)); + kzfree(raw_key); + raw_key = NULL; if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) != NULL) { put_crypt_info(crypt_info); goto retry; @@ -287,7 +297,7 @@ out: if (res == -ENOKEY) res = 0; put_crypt_info(crypt_info); - memzero_explicit(raw_key, sizeof(raw_key)); + kzfree(raw_key); return res; } |