Re: [PATCH -next] drm/amdkfd: Fix NULL pointer dereference in svm_migrate_to_ram()

From: Felix Kuehling
Date: Tue Oct 25 2022 - 15:39:49 EST


Am 2022-10-25 um 03:28 schrieb Yang Li:
./drivers/gpu/drm/amd/amdkfd/kfd_migrate.c:985:58-62: ERROR: p is NULL but dereferenced.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2549
Reported-by: Abaci Robot <abaci@xxxxxxxxxxxxxxxxx>
Signed-off-by: Yang Li <yang.lee@xxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index cddf259875c0..405dd51521dc 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -981,7 +981,8 @@ static vm_fault_t svm_migrate_to_ram(struct vm_fault *vmf)
out_mmput:
mmput(mm);
- pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
+ if (p)
+ pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);

Thank you for catching and reporting this problem. I think the correct solution would be to move the pr_debug up before the kfd_unref_process call. That way you're sure that the pointer is initialized and that it represents a valid reference to the kfd_process structure.

Regards,
  Felix


return r ? VM_FAULT_SIGBUS : 0;
}