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Message-ID: <20170528081249.GD22193@infradead.org>
Date: Sun, 28 May 2017 01:12:49 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Kees Cook <keescook@...omium.org>
Cc: kernel-hardening@...ts.openwall.com,
David Howells <dhowells@...hat.com>,
Laura Abbott <labbott@...hat.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/20] randstruct: Whitelist big_key path struct
overloading
What about the untested patch below to just fix the issue?
---
>From e9eb519c854d2f3d16a4def492577a883246e290 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@....de>
Date: Sun, 28 May 2017 11:03:34 +0300
Subject: security/keys: don't cast union key_payload
Instead store the individual pointers in struct path.
Signed-off-by: Christoph Hellwig <hch@....de>
---
security/keys/big_key.c | 35 ++++++++++++++++++++---------------
1 file changed, 20 insertions(+), 15 deletions(-)
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index 835c1ab30d01..06f2cd07dbd7 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -26,8 +26,8 @@
*/
enum {
big_key_data,
- big_key_path,
- big_key_path_2nd_part,
+ big_key_path_mnt,
+ big_key_path_dentry,
big_key_len,
};
@@ -118,12 +118,16 @@ static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key)
return ret;
}
+#define PATH_FROM_PAYLOAD(p) { \
+ .mnt = (p)->data[big_key_path_mnt], \
+ .dentry = (p)->data[big_key_path_dentry], \
+}
+
/*
* Preparse a big key
*/
int big_key_preparse(struct key_preparsed_payload *prep)
{
- struct path *path = (struct path *)&prep->payload.data[big_key_path];
struct file *file;
u8 *enckey;
u8 *data = NULL;
@@ -190,9 +194,10 @@ int big_key_preparse(struct key_preparsed_payload *prep)
/* Pin the mount and dentry to the key so that we can open it again
* later
*/
+ path_get(&file->f_path);
prep->payload.data[big_key_data] = enckey;
- *path = file->f_path;
- path_get(path);
+ prep->payload.data[big_key_path_mnt] = file->f_path.mnt;
+ prep->payload.data[big_key_path_dentry] = file->f_path.dentry;
fput(file);
kfree(data);
} else {
@@ -222,9 +227,9 @@ int big_key_preparse(struct key_preparsed_payload *prep)
void big_key_free_preparse(struct key_preparsed_payload *prep)
{
if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&prep->payload.data[big_key_path];
+ struct path path = PATH_FROM_PAYLOAD(&prep->payload);
- path_put(path);
+ path_put(&path);
}
kfree(prep->payload.data[big_key_data]);
}
@@ -235,13 +240,13 @@ void big_key_free_preparse(struct key_preparsed_payload *prep)
*/
void big_key_revoke(struct key *key)
{
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path path = PATH_FROM_PAYLOAD(&key->payload);
/* clear the quota */
key_payload_reserve(key, 0);
if (key_is_instantiated(key) &&
(size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
- vfs_truncate(path, 0);
+ vfs_truncate(&path, 0);
}
/*
@@ -252,11 +257,11 @@ void big_key_destroy(struct key *key)
size_t datalen = (size_t)key->payload.data[big_key_len];
if (datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path path = PATH_FROM_PAYLOAD(&key->payload);
- path_put(path);
- path->mnt = NULL;
- path->dentry = NULL;
+ path_put(&path);
+ key->payload.data[big_key_path_mnt] = NULL;
+ key->payload.data[big_key_path_dentry] = NULL;
}
kfree(key->payload.data[big_key_data]);
key->payload.data[big_key_data] = NULL;
@@ -290,7 +295,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
return datalen;
if (datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path path = PATH_FROM_PAYLOAD(&key->payload);
struct file *file;
u8 *data;
u8 *enckey = (u8 *)key->payload.data[big_key_data];
@@ -300,7 +305,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
if (!data)
return -ENOMEM;
- file = dentry_open(path, O_RDONLY, current_cred());
+ file = dentry_open(&path, O_RDONLY, current_cred());
if (IS_ERR(file)) {
ret = PTR_ERR(file);
goto error;
--
2.11.0
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