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authorDavid Howells <dhowells@redhat.com>2011-06-17 11:25:59 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2011-06-17 09:40:48 -0700
commit879669961b11e7f40b518784863a259f735a72bf (patch)
tree9bff5392e365caf656c9dd9be38f7471c182278c /kernel/kmod.c
parenteb96c925152fc289311e5d7e956b919e9b60ab53 (diff)
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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>
Diffstat (limited to 'kernel/kmod.c')
-rw-r--r--kernel/kmod.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c
index ad6a81c58b44..47613dfb7b28 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -156,12 +156,6 @@ static int ____call_usermodehelper(void *data)
*/
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 @@ static int ____call_usermodehelper(void *data)
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 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
* 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)
{