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authorMiroslav Benes <mbenes@suse.cz>2017-12-21 14:40:43 +0100
committerJiri Kosina <jkosina@suse.cz>2018-01-11 17:36:07 +0100
commit8869016d3a58cbe7c31c70f4f008a92122b271c7 (patch)
tree02ebd2a73b91b135034353426d3430e3b28c7832 /kernel/livepatch
parentc99a2be790b07752d8cc694434d3450afd4c5a00 (diff)
downloadlinux-8869016d3a58cbe7c31c70f4f008a92122b271c7.tar.bz2
livepatch: add locking to force and signal functions
klp_send_signals() and klp_force_transition() do not acquire klp_mutex, because it seemed to be superfluous. A potential race in klp_send_signals() was harmless and there was nothing in klp_force_transition() which needed to be synchronized. That changed with the addition of klp_forced variable during the review process. There is a small window now, when klp_complete_transition() does not see klp_forced set to true while all tasks have been already transitioned to the target state. module_put() is called and the module can be removed. Acquire klp_mutex in sysfs callback to prevent it. Do the same for the signal sending just to be sure. There is no real downside to that. Fixes: c99a2be790b07 ("livepatch: force transition to finish") Fixes: 43347d56c8d9d ("livepatch: send a fake signal to all blocking tasks") Reported-by: Jason Baron <jbaron@akamai.com> Signed-off-by: Miroslav Benes <mbenes@suse.cz> Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'kernel/livepatch')
-rw-r--r--kernel/livepatch/core.c52
1 files changed, 28 insertions, 24 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 1c3c9b27c916..8fd8e8f126da 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -537,22 +537,24 @@ static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
int ret;
bool val;
- patch = container_of(kobj, struct klp_patch, kobj);
-
- /*
- * klp_mutex lock is not grabbed here intentionally. It is not really
- * needed. The race window is harmless and grabbing the lock would only
- * hold the action back.
- */
- if (patch != klp_transition_patch)
- return -EINVAL;
-
ret = kstrtobool(buf, &val);
if (ret)
return ret;
- if (val)
- klp_send_signals();
+ if (!val)
+ return count;
+
+ mutex_lock(&klp_mutex);
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ if (patch != klp_transition_patch) {
+ mutex_unlock(&klp_mutex);
+ return -EINVAL;
+ }
+
+ klp_send_signals();
+
+ mutex_unlock(&klp_mutex);
return count;
}
@@ -564,22 +566,24 @@ static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
int ret;
bool val;
- patch = container_of(kobj, struct klp_patch, kobj);
-
- /*
- * klp_mutex lock is not grabbed here intentionally. It is not really
- * needed. The race window is harmless and grabbing the lock would only
- * hold the action back.
- */
- if (patch != klp_transition_patch)
- return -EINVAL;
-
ret = kstrtobool(buf, &val);
if (ret)
return ret;
- if (val)
- klp_force_transition();
+ if (!val)
+ return count;
+
+ mutex_lock(&klp_mutex);
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ if (patch != klp_transition_patch) {
+ mutex_unlock(&klp_mutex);
+ return -EINVAL;
+ }
+
+ klp_force_transition();
+
+ mutex_unlock(&klp_mutex);
return count;
}