[PATCH v2] drm/panthor: Fix potential memleak of vma structure

[Akash Goel]

This commit addresses a memleak issue of panthor_vma (or drm_gpuva)
structure in Panthor driver, that can happen if the GPU page table
update operation to map the pages fail.
The issue is very unlikely to occur in practice.

v2: Add panthor_vm_op_ctx_return_vma() helper (Boris)

Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Signed-off-by: Akash Goel <akash.g...@arm.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c 
b/drivers/gpu/drm/panthor/panthor_mmu.c
index 6dec4354e378..63af8ee89b08 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1146,6 +1146,18 @@ static void panthor_vm_cleanup_op_ctx(struct 
panthor_vm_op_ctx *op_ctx,
        }
 }
 
+static void
+panthor_vm_op_ctx_return_vma(struct panthor_vm_op_ctx *op_ctx,
+                            struct panthor_vma *vma)
+{
+       for (u32 i = 0; i < ARRAY_SIZE(op_ctx->preallocated_vmas); i++) {
+               if (!op_ctx->preallocated_vmas[i]) {
+                       op_ctx->preallocated_vmas[i] = vma;
+                       return;
+               }
+       }
+}
+
 static struct panthor_vma *
 panthor_vm_op_ctx_get_vma(struct panthor_vm_op_ctx *op_ctx)
 {
@@ -2081,8 +2093,10 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op 
*op, void *priv)
        ret = panthor_vm_map_pages(vm, op->map.va.addr, 
flags_to_prot(vma->flags),
                                   op_ctx->map.sgt, op->map.gem.offset,
                                   op->map.va.range);
-       if (ret)
+       if (ret) {
+               panthor_vm_op_ctx_return_vma(op_ctx, vma);
                return ret;
+       }
 
        /* Ref owned by the mapping now, clear the obj field so we don't 
release the
         * pinning/obj ref behind GPUVA's back.
-- 
2.25.1