[PATCH AUTOSEL 5.7 104/274] drm/ast: Allocate initial CRTC state of the correct size

Sasha Levin
2020-06-09T00:59:55Z

From: Thomas Zimmermann <tzimmermann@suse.de>

[ Upstream commit f0adbc382b8bb46a2467c4e5e1027763a197c8e1 ]

The ast driver inherits from DRM's CRTC state, but still uses the atomic
helper for struct drm_crtc_funcs.reset, drm_atomic_helper_crtc_reset().

The helper only allocates enough memory for the core CRTC state. That
results in an out-ouf-bounds access when duplicating the initial CRTC
state. Simplified backtrace shown below:

[ 21.469321] ==================================================================
[ 21.469434] BUG: KASAN: slab-out-of-bounds in ast_crtc_atomic_duplicate_state+0x84/0x100 [ast]
[ 21.469445] Read of size 8 at addr ffff888036c1c5f8 by task systemd-udevd/382
[ 21.469451]
[ 21.469464] CPU: 2 PID: 382 Comm: systemd-udevd Tainted: G E 5.5.0-rc6-1-default+ #214
[ 21.469473] Hardware name: Sun Microsystems SUN FIRE X2270 M2/SUN FIRE X2270 M2, BIOS 2.05 07/01/2010
[ 21.469480] Call Trace:
[ 21.469501] dump_stack+0xb8/0x110
[ 21.469528] print_address_description.constprop.0+0x1b/0x1e0
[ 21.469557] ? ast_crtc_atomic_duplicate_state+0x84/0x100 [ast]
[ 21.469581] ? ast_crtc_atomic_duplicate_state+0x84/0x100 [ast]
[ 21.469597] __kasan_report.cold+0x1a/0x35
[ 21.469640] ? ast_crtc_atomic_duplicate_state+0x84/0x100 [ast]
[ 21.469665] kasan_report+0xe/0x20
[ 21.469693] ast_crtc_atomic_duplicate_state+0x84/0x100 [ast]
[ 21.469733] drm_atomic_get_crtc_state+0xbf/0x1c0
[ 21.469768] __drm_atomic_helper_set_config+0x81/0x5a0
[ 21.469803] ? drm_atomic_plane_check+0x690/0x690
[ 21.469843] ? drm_client_rotation+0xae/0x240
[ 21.469876] drm_client_modeset_commit_atomic+0x230/0x390
[ 21.469888] ? __mutex_lock+0x8f0/0xbe0
[ 21.469929] ? drm_client_firmware_config.isra.0+0xa60/0xa60
[ 21.469948] ? drm_client_modeset_commit_force+0x28/0x230
[ 21.470031] ? memset+0x20/0x40
[ 21.470078] drm_client_modeset_commit_force+0x90/0x230
[ 21.470110] drm_fb_helper_restore_fbdev_mode_unlocked+0x5f/0xc0
[ 21.470132] drm_fb_helper_set_par+0x59/0x70
[ 21.470155] fbcon_init+0x61d/0xad0
[ 21.470185] ? drm_fb_helper_restore_fbdev_mode_unlocked+0xc0/0xc0
[ 21.470232] visual_init+0x187/0x240
[ 21.470266] do_bind_con_driver+0x2e3/0x460
[ 21.470321] do_take_over_console+0x20a/0x290
[ 21.470371] do_fbcon_takeover+0x85/0x100
[ 21.470402] register_framebuffer+0x2fd/0x490
[ 21.470425] ? kzalloc.constprop.0+0x10/0x10
[ 21.470503] __drm_fb_helper_initial_config_and_unlock+0xf2/0x140
[ 21.470533] drm_fbdev_client_hotplug+0x162/0x250
[ 21.470563] drm_fbdev_generic_setup+0xd2/0x155
[ 21.470602] ast_driver_load+0x688/0x850 [ast]
<...>
[ 21.472625] ==================================================================

Allocating enough memory for struct ast_crtc_state in a custom ast CRTC
reset handler fixes the problem.

v2:
* implement according to drm_atomic_helper_crtc_reset()
* update state with __drm_atomic_helper_crtc_reset()

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 83be6a3ceb11 ("drm/ast: Introduce struct ast_crtc_state")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200130094012.32140-1-tzimmermann@suse.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/ast/ast_mode.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index cdd6c46d6557..7a9f20a2fd30 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -881,6 +881,17 @@ static const struct drm_crtc_helper_funcs ast_crtc_helper_funcs = {
.atomic_disable = ast_crtc_helper_atomic_disable,
};

+static void ast_crtc_reset(struct drm_crtc *crtc)
+{
+ struct ast_crtc_state *ast_state =
+ kzalloc(sizeof(*ast_state), GFP_KERNEL);
+
+ if (crtc->state)
+ crtc->funcs->atomic_destroy_state(crtc, crtc->state);
+
+ __drm_atomic_helper_crtc_reset(crtc, &ast_state->base);
+}
+
static void ast_crtc_destroy(struct drm_crtc *crtc)
{
drm_crtc_cleanup(crtc);
@@ -919,7 +930,7 @@ static void ast_crtc_atomic_destroy_state(struct drm_crtc *crtc,
}

static const struct drm_crtc_funcs ast_crtc_funcs = {
- .reset = drm_atomic_helper_crtc_reset,
+ .reset = ast_crtc_reset,
.set_config = drm_crtc_helper_set_config,
.gamma_set = drm_atomic_helper_legacy_gamma_set,
.destroy = ast_crtc_destroy,
--
2.25.1