From b9edd74ee0baadeadc573142581769da76a3965e Mon Sep 17 00:00:00 2001
From: Philip Yang <Philip.Yang@amd.com>
Date: Wed, 20 Jul 2022 18:00:45 -0400
Subject: drm/amdkfd: Correct mmu_notifier_get failure handling
Git-commit: 0593ad215359d51514c1e6c81ce28ea598efed6b
Patch-mainline: v6.0-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
If process has signal pending, mmu_notifier_get_locked fails and calls
ops->free_notifier, kfd_process_free_notifier will schedule
kfd_process_wq_release as process refcount is 1, but process structure
is already freed. This use after free bug causes system crash with
different backtrace.
The fix is to increase process refcount and then decrease the refcount
after mmu_notifier_get success.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index fc38a4d81420..d8591721270b 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1405,6 +1405,11 @@ static struct kfd_process *create_process(const struct task_struct *thread)
hash_add_rcu(kfd_processes_table, &process->kfd_processes,
(uintptr_t)process->mm);
+ /* Avoid free_notifier to start kfd_process_wq_release if
+ * mmu_notifier_get failed because of pending signal.
+ */
+ kref_get(&process->ref);
+
/* MMU notifier registration must be the last call that can fail
* because after this point we cannot unwind the process creation.
* After this point, mmu_notifier_put will trigger the cleanup by
@@ -1417,6 +1422,7 @@ static struct kfd_process *create_process(const struct task_struct *thread)
}
BUG_ON(mn != &process->mmu_notifier);
+ kfd_unref_process(process);
get_task_struct(process->lead_thread);
return process;
--
2.38.1