The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From a6e08912861757b8b335cc49b093a51ec025c5de Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Sun, 13 Nov 2016 20:41:09 -0500
Subject: [PATCH] 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@xxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
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 @@ int get_crypt_info(struct inode *inode)
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 @@ int get_crypt_info(struct inode *inode)
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 @@ int get_crypt_info(struct inode *inode)
if (res == -ENOKEY)
res = 0;
put_crypt_info(crypt_info);
- memzero_explicit(raw_key, sizeof(raw_key));
+ kzfree(raw_key);
return res;
}
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