KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring
____call_usermodehelper() now erases any credentials set by the
subprocess_inf::init() function. The problem is that commit
17f60a7da150 ("capabilites: allow the application of capability limits
to usermode helpers") creates and commits new credentials with
prepare_kernel_cred() after the call to the init() function. This wipes
all keyrings after umh_keys_init() is called.
The best way to deal with this is to put the init() call just prior to
the commit_creds() call, and pass the cred pointer to init(). That
means that umh_keys_init() and suchlike can modify the credentials
_before_ they are published and potentially in use by the rest of the
system.
This prevents request_key() from working as it is prevented from passing
the session keyring it set up with the authorisation token to
/sbin/request-key, and so the latter can't assume the authority to
instantiate the key. This causes the in-kernel DNS resolver to fail
with ENOKEY unconditionally.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Tested-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/exec.c b/fs/exec.c
index 97e0d52..6075a1e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1996,7 +1996,7 @@
* is a special value that we use to trap recursive
* core dumps
*/
-static int umh_pipe_setup(struct subprocess_info *info)
+static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
{
struct file *rp, *wp;
struct fdtable *fdt;
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index d4a5c84..0da38cf 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -45,7 +45,7 @@
#endif
-struct key;
+struct cred;
struct file;
enum umh_wait {
@@ -62,7 +62,7 @@
char **envp;
enum umh_wait wait;
int retval;
- int (*init)(struct subprocess_info *info);
+ int (*init)(struct subprocess_info *info, struct cred *new);
void (*cleanup)(struct subprocess_info *info);
void *data;
};
@@ -73,7 +73,7 @@
/* Set various pieces of state into the subprocess_info structure */
void call_usermodehelper_setfns(struct subprocess_info *info,
- int (*init)(struct subprocess_info *info),
+ int (*init)(struct subprocess_info *info, struct cred *new),
void (*cleanup)(struct subprocess_info *info),
void *data);
@@ -87,7 +87,7 @@
static inline int
call_usermodehelper_fns(char *path, char **argv, char **envp,
enum umh_wait wait,
- int (*init)(struct subprocess_info *info),
+ int (*init)(struct subprocess_info *info, struct cred *new),
void (*cleanup)(struct subprocess_info *), void *data)
{
struct subprocess_info *info;
diff --git a/kernel/kmod.c b/kernel/kmod.c
index ad6a81c..47613df 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -156,12 +156,6 @@
*/
set_user_nice(current, 0);
- if (sub_info->init) {
- retval = sub_info->init(sub_info);
- if (retval)
- goto fail;
- }
-
retval = -ENOMEM;
new = prepare_kernel_cred(current);
if (!new)
@@ -173,6 +167,14 @@
new->cap_inheritable);
spin_unlock(&umh_sysctl_lock);
+ if (sub_info->init) {
+ retval = sub_info->init(sub_info, new);
+ if (retval) {
+ abort_creds(new);
+ goto fail;
+ }
+ }
+
commit_creds(new);
retval = kernel_execve(sub_info->path,
@@ -388,7 +390,7 @@
* context in which call_usermodehelper_exec is called.
*/
void call_usermodehelper_setfns(struct subprocess_info *info,
- int (*init)(struct subprocess_info *info),
+ int (*init)(struct subprocess_info *info, struct cred *new),
void (*cleanup)(struct subprocess_info *info),
void *data)
{
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index d31862e..8e319a4 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -71,9 +71,8 @@
* This is called in context of freshly forked kthread before kernel_execve(),
* so we can simply install the desired session_keyring at this point.
*/
-static int umh_keys_init(struct subprocess_info *info)
+static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
{
- struct cred *cred = (struct cred*)current_cred();
struct key *keyring = info->data;
return install_session_keyring_to_cred(cred, keyring);