From: Petr Mladek <pmladek@suse.com>
To: Jiri Kosina <jikos@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Miroslav Benes <mbenes@suse.cz>
Cc: Joe Lawrence <joe.lawrence@redhat.com>,
Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
Nicolai Stange <nstange@suse.de>,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Petr Mladek <pmladek@suse.com>
Subject: [POC 09/23] livepatch: Handle race when livepatches are reloaded during a module load
Date: Fri, 17 Jan 2020 16:03:09 +0100 [thread overview]
Message-ID: <20200117150323.21801-10-pmladek@suse.com> (raw)
In-Reply-To: <20200117150323.21801-1-pmladek@suse.com>
klp_module_coming() might fail to load a livepatch module when
the related livepatch gets reloaded in the meantime.
Detect this situation by adding a timestamp into struct klp_patch.
local_clock is enough because klp_mutex must be released and taken
several times during this scenario.
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
include/linux/livepatch.h | 2 ++
kernel/livepatch/core.c | 9 +++++----
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index a4567c17a9f2..feb33f023f9f 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -155,6 +155,7 @@ struct klp_state {
* @obj_list: dynamic list of the object entries
* @enabled: the patch is enabled (but operation may be incomplete)
* @forced: was involved in a forced transition
+ * ts: timestamp when the livepatch has been loaded
* @free_work: patch cleanup from workqueue-context
* @finish: for waiting till it is safe to remove the patch module
*/
@@ -171,6 +172,7 @@ struct klp_patch {
struct list_head obj_list;
bool enabled;
bool forced;
+ u64 ts;
struct work_struct free_work;
struct completion finish;
};
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 34e3ee2be7ef..8e693c58b736 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -20,6 +20,7 @@
#include <linux/moduleloader.h>
#include <linux/completion.h>
#include <linux/memory.h>
+#include <linux/sched/clock.h>
#include <asm/cacheflush.h>
#include "core.h"
#include "patch.h"
@@ -854,6 +855,7 @@ static int klp_init_patch_early(struct klp_patch *patch)
kobject_init(&patch->kobj, &klp_ktype_patch);
patch->enabled = false;
patch->forced = false;
+ patch->ts = local_clock();
INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
init_completion(&patch->finish);
@@ -1324,6 +1326,7 @@ int klp_module_coming(struct module *mod)
{
char patch_name[MODULE_NAME_LEN];
struct klp_patch *patch;
+ u64 patch_ts;
int ret = 0;
if (WARN_ON(mod->state != MODULE_STATE_COMING))
@@ -1339,6 +1342,7 @@ int klp_module_coming(struct module *mod)
continue;
strncpy(patch_name, patch->obj->patch_name, sizeof(patch_name));
+ patch_ts = patch->ts;
mutex_unlock(&klp_mutex);
ret = klp_try_load_object(patch_name, mod->name);
@@ -1346,14 +1350,11 @@ int klp_module_coming(struct module *mod)
* The load might have failed because the patch has
* been removed in the meantime. In this case, the
* error might be ignored.
- *
- * FIXME: It is not fully proof. The patch might have be
- * unloaded and loaded again in the mean time.
*/
mutex_lock(&klp_mutex);
if (ret) {
patch = klp_find_patch(patch_name);
- if (patch)
+ if (patch && patch->ts == patch_ts)
goto err;
ret = 0;
}
--
2.16.4
next prev parent reply other threads:[~2020-01-17 15:05 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 15:03 [POC 00/23] livepatch: Split livepatch module per-object Petr Mladek
2020-01-17 15:03 ` [POC 01/23] module: Allow to delete module also from inside kernel Petr Mladek
2020-01-21 11:11 ` Julien Thierry
2020-01-17 15:03 ` [POC 02/23] livepatch: Split livepatch modules per livepatched object Petr Mladek
2020-01-21 11:11 ` Julien Thierry
2020-01-28 12:16 ` Petr Mladek
2020-01-17 15:03 ` [POC 03/23] livepatch: Better checks of struct klp_object definition Petr Mladek
2020-01-21 11:27 ` Julien Thierry
2020-01-17 15:03 ` [POC 04/23] livepatch: Prevent loading livepatch sub-module unintentionally Petr Mladek
2020-04-03 17:54 ` Joe Lawrence
2020-01-17 15:03 ` [POC 05/23] livepatch: Initialize and free livepatch submodule Petr Mladek
2020-01-21 11:58 ` Julien Thierry
2020-01-17 15:03 ` [POC 06/23] livepatch: Enable the " Petr Mladek
2020-01-17 15:03 ` [POC 07/23] livepatch: Remove obsolete functionality from klp_module_coming() Petr Mladek
2020-01-17 15:03 ` [POC 08/23] livepatch: Automatically load livepatch module when the patch module is loaded Petr Mladek
2020-01-17 15:03 ` Petr Mladek [this message]
2020-01-22 18:51 ` [POC 09/23] livepatch: Handle race when livepatches are reloaded during a module load Julien Thierry
2020-01-17 15:03 ` [POC 10/23] livepatch: Handle modprobe exit code Petr Mladek
2020-01-17 15:03 ` [POC 11/23] livepatch: Safely detect forced transition when removing split livepatch modules Petr Mladek
2020-01-22 10:15 ` Julien Thierry
2020-01-17 15:03 ` [POC 12/23] livepatch: Automatically remove livepatch module when the object is freed Petr Mladek
2020-01-17 15:03 ` [POC 13/23] livepatch: Remove livepatch module when the livepatched module is unloaded Petr Mladek
2020-01-17 15:03 ` [POC 14/23] livepatch: Never block livepatch modules when the related module is being removed Petr Mladek
2020-01-17 15:03 ` [POC 15/23] livepatch: Prevent infinite loop when loading livepatch module Petr Mladek
2020-01-17 15:03 ` [POC 16/23] livepatch: Add patch into the global list early Petr Mladek
2020-01-17 15:03 ` [POC 17/23] livepatch: Load livepatches for modules when loading the main livepatch Petr Mladek
2020-01-17 15:03 ` [POC 18/23] module: Refactor add_unformed_module() Petr Mladek
2020-01-17 15:03 ` [POC 19/23] module/livepatch: Allow to use exported symbols from livepatch module for "vmlinux" Petr Mladek
2020-04-06 18:48 ` Joe Lawrence
2020-04-07 7:33 ` Miroslav Benes
2020-04-07 20:57 ` Joe Lawrence
2020-01-17 15:03 ` [POC 20/23] module/livepatch: Relocate local variables in the module loaded when the livepatch is being loaded Petr Mladek
2020-01-18 10:29 ` kbuild test robot
2020-04-03 18:00 ` Joe Lawrence
2020-01-17 15:03 ` [POC 21/23] livepatch: Remove obsolete arch_klp_init_object_loaded() Petr Mladek
2020-01-17 15:03 ` [POC 22/23] livepatch/module: Remove obsolete copy_module_elf() Petr Mladek
2020-04-03 18:03 ` Joe Lawrence
2020-01-17 15:03 ` [POC 23/23] module: Remove obsolete module_disable_ro() Petr Mladek
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