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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
17f60a7da1
("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>
This commit is contained in:
parent
eb96c92515
commit
879669961b
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@ -1996,7 +1996,7 @@ static void wait_for_dump_helpers(struct file *file)
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* is a special value that we use to trap recursive
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* core dumps
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*/
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static int umh_pipe_setup(struct subprocess_info *info)
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static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
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{
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struct file *rp, *wp;
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struct fdtable *fdt;
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@ -45,7 +45,7 @@ static inline int request_module_nowait(const char *name, ...) { return -ENOSYS;
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#endif
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struct key;
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struct cred;
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struct file;
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enum umh_wait {
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@ -62,7 +62,7 @@ struct subprocess_info {
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char **envp;
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enum umh_wait wait;
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int retval;
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int (*init)(struct subprocess_info *info);
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int (*init)(struct subprocess_info *info, struct cred *new);
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void (*cleanup)(struct subprocess_info *info);
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void *data;
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};
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@ -73,7 +73,7 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
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/* Set various pieces of state into the subprocess_info structure */
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void call_usermodehelper_setfns(struct subprocess_info *info,
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int (*init)(struct subprocess_info *info),
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int (*init)(struct subprocess_info *info, struct cred *new),
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void (*cleanup)(struct subprocess_info *info),
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void *data);
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@ -87,7 +87,7 @@ void call_usermodehelper_freeinfo(struct subprocess_info *info);
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static inline int
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call_usermodehelper_fns(char *path, char **argv, char **envp,
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enum umh_wait wait,
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int (*init)(struct subprocess_info *info),
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int (*init)(struct subprocess_info *info, struct cred *new),
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void (*cleanup)(struct subprocess_info *), void *data)
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{
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struct subprocess_info *info;
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@ -156,12 +156,6 @@ static int ____call_usermodehelper(void *data)
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*/
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set_user_nice(current, 0);
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if (sub_info->init) {
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retval = sub_info->init(sub_info);
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if (retval)
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goto fail;
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}
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retval = -ENOMEM;
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new = prepare_kernel_cred(current);
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if (!new)
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@ -173,6 +167,14 @@ static int ____call_usermodehelper(void *data)
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new->cap_inheritable);
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spin_unlock(&umh_sysctl_lock);
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if (sub_info->init) {
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retval = sub_info->init(sub_info, new);
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if (retval) {
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abort_creds(new);
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goto fail;
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}
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}
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commit_creds(new);
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retval = kernel_execve(sub_info->path,
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@ -388,7 +390,7 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
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* context in which call_usermodehelper_exec is called.
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*/
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void call_usermodehelper_setfns(struct subprocess_info *info,
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int (*init)(struct subprocess_info *info),
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int (*init)(struct subprocess_info *info, struct cred *new),
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void (*cleanup)(struct subprocess_info *info),
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void *data)
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{
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@ -71,9 +71,8 @@ EXPORT_SYMBOL(complete_request_key);
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* This is called in context of freshly forked kthread before kernel_execve(),
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* so we can simply install the desired session_keyring at this point.
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*/
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static int umh_keys_init(struct subprocess_info *info)
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static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
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{
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struct cred *cred = (struct cred*)current_cred();
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struct key *keyring = info->data;
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return install_session_keyring_to_cred(cred, keyring);
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