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Subject[PATCH -repost 18/21] kgr: fix race of stub and patching
Date
While we are patching, we set up a stub which refers to
kgr_in_progress of a process. The stub can be called immediately when
set up, but we set the flag even after done with patching in
kgr_handle_processes. This is obviously too late, so set the flag
before we start patching, but after we check that no other patching is
in progress -- we would interfere otherwise.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
---
kernel/kgraft.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/kgraft.c b/kernel/kgraft.c
index 121faefcbb28..5ec0c1abe0d6 100644
--- a/kernel/kgraft.c
+++ b/kernel/kgraft.c
@@ -124,14 +124,22 @@ static void kgr_work_fn(struct work_struct *work)
mutex_unlock(&kgr_in_progress_lock);
}

-static void kgr_handle_processes(void)
+static void kgr_mark_processes(void)
{
struct task_struct *p;

read_lock(&tasklist_lock);
- for_each_process(p) {
+ for_each_process(p)
kgr_mark_task_in_progress(p);
+ read_unlock(&tasklist_lock);
+}

+static void kgr_handle_processes(void)
+{
+ struct task_struct *p;
+
+ read_lock(&tasklist_lock);
+ for_each_process(p) {
/* wake up kthreads, they will clean the progress flag */
if (!p->mm) {
/*
@@ -333,6 +341,8 @@ int kgr_start_patching(struct kgr_patch *patch)
goto unlock_free;
}

+ kgr_mark_processes();
+
for (patch_fun = patch->patches; *patch_fun; patch_fun++) {
ret = kgr_patch_code(patch, *patch_fun, false);
/*
--
2.0.0


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