[PATCH] drm/amdkfd: Fix a wild pointer dereference in svm_range_add()

[Zhou Qingyang]

In svm_range_add(), the return value of svm_range_new() is assigned
to prange and &prange->insert_list is used in list_add(). There is a
a dereference of &prange->insert_list in list_add(), which could lead
to a wild pointer dereference on failure of vm_range_new() if
CONFIG_DEBUG_LIST is unset in .config file.

Fix this bug by adding a check of prange.

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_DRM_AMDGPU=m, CONFIG_HSA_AMD=y, and
CONFIG_HSA_AMD_SVM=y show no new warnings, and our static analyzer no
longer warns about this code.

Fixes: 42de677f7999 ("drm/amdkfd: register svm range")
Signed-off-by: Zhou Qingyang <zhou1615@xxxxxxx>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 58b89b53ebe6..e40c2211901d 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -2940,6 +2940,9 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
 
 	if (left) {
 		prange = svm_range_new(svms, last - left + 1, last);
+		if (!prange)
+			return -ENOMEM;
+
 		list_add(&prange->insert_list, insert_list);
 		list_add(&prange->update_list, update_list);
 	}
-- 
2.25.1