The firmware exposes the global group count and per-group stream count in the shared control interface. These values are validated before being used as loop bounds.
Read each count once with READ_ONCE() and store it in a local variable. This avoids reading the same control section field twice and makes it explicit that the loop uses the same value that passed validation to protect against self-modifying control sections. Signed-off-by: Osama Abdelkader <[email protected]> Reviewed-by: Steven Price <[email protected]> --- v3: - Add comments explaining the READ_ONCE() usage. drivers/gpu/drm/panthor/panthor_fw.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c index 8411c468bdac..b2ccb81f280c 100644 --- a/drivers/gpu/drm/panthor/panthor_fw.c +++ b/drivers/gpu/drm/panthor/panthor_fw.c @@ -954,6 +954,7 @@ static int panthor_init_csg_iface(struct panthor_device *ptdev, u64 shared_section_sz = panthor_kernel_bo_size(ptdev->fw->shared_section->mem); u64 iface_offset = CSF_GROUP_CONTROL_OFFSET + ((u64)csg_idx * glb_iface->control->group_stride); + u32 stream_num; unsigned int i; if (iface_offset > shared_section_sz || @@ -967,8 +968,13 @@ static int panthor_init_csg_iface(struct panthor_device *ptdev, csg_iface->output = iface_fw_to_cpu_addr(ptdev, csg_iface->control->output_va, sizeof(*csg_iface->output)); - if (csg_iface->control->stream_num < MIN_CS_PER_CSG || - csg_iface->control->stream_num > MAX_CS_PER_CSG) + /* + * To protect against self-modifying control sections + * take a single snapshot from the control section so validation and + * iteration use the same value. + */ + stream_num = READ_ONCE(csg_iface->control->stream_num); + if (stream_num < MIN_CS_PER_CSG || stream_num > MAX_CS_PER_CSG) return -EINVAL; if (!csg_iface->input || !csg_iface->output) { @@ -986,7 +992,7 @@ static int panthor_init_csg_iface(struct panthor_device *ptdev, } } - for (i = 0; i < csg_iface->control->stream_num; i++) { + for (i = 0; i < stream_num; i++) { int ret = panthor_init_cs_iface(ptdev, csg_idx, i); if (ret) @@ -1010,6 +1016,7 @@ static int panthor_fw_init_ifaces(struct panthor_device *ptdev) { struct panthor_fw_global_iface *glb_iface = &ptdev->fw->iface.global; u64 shared_section_sz = panthor_kernel_bo_size(ptdev->fw->shared_section->mem); + u32 group_num; unsigned int i; if (!ptdev->fw->shared_section->mem->kmap) @@ -1035,13 +1042,18 @@ static int panthor_fw_init_ifaces(struct panthor_device *ptdev) return -EINVAL; } - if (glb_iface->control->group_num > MAX_CSGS || - glb_iface->control->group_num < MIN_CSGS) { + /* + * To protect against self-modifying control sections + * take a single snapshot from the control section so validation and + * iteration use the same value. + */ + group_num = READ_ONCE(glb_iface->control->group_num); + if (group_num > MAX_CSGS || group_num < MIN_CSGS) { drm_err(&ptdev->base, "Invalid number of control groups"); return -EINVAL; } - for (i = 0; i < glb_iface->control->group_num; i++) { + for (i = 0; i < group_num; i++) { int ret = panthor_init_csg_iface(ptdev, i); if (ret) -- 2.43.0
