[SRU][R][PATCH 1/1] drm/amdkfd: fix kernel crash on releasing NULL sysfs entry

[Woongjun Choi]

From: Eric Huang <jinhuieric.huang at amd.com>

BugLink: https://bugs.launchpad.net/bugs/2168705

there is an abnormal case that When a process re-opens kfd
with different mm_struct(execve() called by user), the
allocated p->kobj will be freed, but missed setting it to NULL,
that will cause sysfs/kernel crash with NULL pointers in p->kobj
on kfd_process_remove_sysfs() when releasing process, and the
similar error on kfd_procfs_del_queue() as well.

Signed-off-by: Eric Huang <jinhuieric.huang at amd.com>
Reviewed-by: Kent Russell <kent.russell at amd.com>
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
(cherry picked from commit 4ea64d482fc2cc85009fce5abdf4780ece00c31c)
Signed-off-by: Woongjun Choi <oongjoon10 at gmail.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_process.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index fcda5ef..4b2fa74 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -679,7 +679,7 @@ static void kfd_procfs_add_sysfs_files(struct kfd_process *p)
 
 void kfd_procfs_del_queue(struct queue *q)
 {
-	if (!q)
+	if (!q || !q->process->kobj)
 		return;
 
 	kobject_del(&q->kobj);
@@ -858,6 +858,7 @@ int kfd_create_process_sysfs(struct kfd_process *process)
 	if (ret) {
 		pr_warn("Creating procfs pid directory failed");
 		kobject_put(process->kobj);
+		process->kobj = NULL;
 		return ret;
 	}
 
-- 
2.53.0