[PATCH 5/5] drm/amdgpu: free userptr HMM ranges on the CS error path

[Junrui Luo via B4 Relay]

From: Junrui Luo <moonafterrain@xxxxxxxxxxx>

amdgpu_cs_parser_bos() allocates a struct amdgpu_hmm_range for every
userptr entry of the BO list and returns with them live. They are only
released in two places: the out_free_user_pages label in
amdgpu_cs_parser_bos() itself, and the invalidation check loop in
amdgpu_cs_submit().

Every error edge between those two points leaks. A failure in
amdgpu_cs_patch_jobs(), amdgpu_cs_vm_handling() or amdgpu_cs_sync_rings(),
or an early return from amdgpu_cs_submit() before its release loop, jumps
to error_fini and falls into amdgpu_cs_parser_fini(), which never walks
the BO list for userptr ranges. An IB address with no VM mapping is enough
to get there: amdgpu_cs_patch_ibs() returns the -EINVAL that
amdgpu_cs_find_mapping() hands back, so the leak is repeatable at will
from an unprivileged render node fd. Each leaked entry costs a struct
amdgpu_hmm_range plus its hmm_pfns array, a kvmalloc_array() of one entry
per page of the userptr mapping, allocated with plain GFP_KERNEL and so
not charged to the caller's memory cgroup.

Release the ranges in amdgpu_cs_parser_fini(), which every path out of
amdgpu_cs_ioctl() passes through. amdgpu_hmm_range_free() ignores a NULL
range, so the success path, where amdgpu_cs_submit() has already freed and
cleared them, is unaffected.

Fixes: fec8fdb54e8f ("drm/amdgpu: fix userptr HMM range handling v2")
Reported-by: Yuhao Jiang <danisjiang@xxxxxxxxx>
Assisted-by: Claude:claude-opus-5
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Junrui Luo <moonafterrain@xxxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 617f53f135f3..17c4fec21402 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1416,6 +1416,16 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser)
 				amdgpu_vm_bo_invalidate(bo, false);
 			}
 		}
+
+		/*
+		 * Release the ranges still live on the error paths;
+		 * amdgpu_cs_submit() already freed and cleared them when it
+		 * got far enough to check them for invalidation.
+		 */
+		amdgpu_bo_list_for_each_userptr_entry(e, parser->bo_list) {
+			amdgpu_hmm_range_free(e->range);
+			e->range = NULL;
+		}
 		amdgpu_bo_list_put(parser->bo_list);
 	}
 

-- 
2.51.2