From 17e2030f37600994440f875dc410615d5c66ee6d Mon Sep 17 00:00:00 2001 From: Icenowy Zheng Date: Tue, 14 Jul 2026 15:36:41 +0800 Subject: [PATCH] drm/imagination: acquire vm_ctx->lock before mapping memory to GPU VM The drm gpuvm code doesn't protect find operation against map operation, and the driver needs to ensure a map operation shouldn't happen when a find operation is in progress. In some cases a find operation will be in progress when doing map/unmap operations, and the find operation will do a NULL pointer dereference. An example of the stack trace of such NULL dereference is shown below: ``` Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000000010 [] drm_gpuva_find+0x28/0x6c [drm_gpuvm] [] pvr_vm_unmap+0x34/0x68 [powervr] [] pvr_ioctl_vm_unmap+0x2e/0x50 [powervr] [] drm_ioctl_kernel+0x8e/0xdc [] drm_ioctl+0x1be/0x3e0 [] __riscv_sys_ioctl+0xba/0xc4 [] do_trap_ecall_u+0x23e/0x3f4 [] handle_exception+0x168/0x174 ``` As all occurences of drm_gpuva_find*() are already guarded by vm_ctx->lock, make pvr_vm_map() to acquire this lock to prevent disturbing any find operation. This fixes the NULL deference problem in drm_gpuva_find*(). Cc: stable@vger.kernel.org Fixes: ff5f643de0bf ("drm/imagination: Add GEM and VM related code") Fixes: 4bc736f890ce ("drm/imagination: vm: make use of GPUVM's drm_exec helper") Signed-off-by: Icenowy Zheng Reviewed-by: Alessio Belle Link: https://patch.msgid.link/20260714073641.1935075-1-zhengxingda@iscas.ac.cn Signed-off-by: Alessio Belle --- drivers/gpu/drm/imagination/pvr_vm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/imagination/pvr_vm.c b/drivers/gpu/drm/imagination/pvr_vm.c index 396d349fb6ce..ceb78694cd98 100644 --- a/drivers/gpu/drm/imagination/pvr_vm.c +++ b/drivers/gpu/drm/imagination/pvr_vm.c @@ -747,6 +747,7 @@ pvr_vm_map(struct pvr_vm_context *vm_ctx, struct pvr_gem_object *pvr_obj, pvr_gem_object_get(pvr_obj); + mutex_lock(&vm_ctx->lock); err = drm_gpuvm_exec_lock(&vm_exec); if (err) goto err_cleanup; @@ -756,6 +757,7 @@ pvr_vm_map(struct pvr_vm_context *vm_ctx, struct pvr_gem_object *pvr_obj, drm_gpuvm_exec_unlock(&vm_exec); err_cleanup: + mutex_unlock(&vm_ctx->lock); pvr_vm_bind_op_fini(&bind_op); return err;