From ff89e507b231a3afbddc2972a850947b73247a3b Mon Sep 17 00:00:00 2001 From: Ziqi Zhao Date: Fri, 21 Jul 2023 09:14:46 -0700 Subject: [PATCH] drm/crtc: Fix uninit-value bug in drm_mode_setcrtc [ Upstream commit 3823119b9c2b5f9e9b760336f75bc989b805cde6 ] The connector_set contains uninitialized values when allocated with kmalloc_array. However, in the "out" branch, the logic assumes that any element in connector_set would be equal to NULL if failed to initialize, which causes the bug reported by Syzbot. The fix is to use an extra variable to keep track of how many connectors are initialized indeed, and use that variable to decrease any refcounts in the "out" branch. Reported-by: syzbot+4fad2e57beb6397ab2fc@syzkaller.appspotmail.com Signed-off-by: Ziqi Zhao Reported-and-tested-by: syzbot+4fad2e57beb6397ab2fc@syzkaller.appspotmail.com Tested-by: Harshit Mogalapalli Link: https://lore.kernel.org/r/20230721161446.8602-1-astrajoan@yahoo.com Signed-off-by: Maxime Ripard Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_crtc.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index df9bf3c..d718c17 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -715,8 +715,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, struct drm_mode_set set; uint32_t __user *set_connectors_ptr; struct drm_modeset_acquire_ctx ctx; - int ret; - int i; + int ret, i, num_connectors; if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; @@ -851,6 +850,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, goto out; } + num_connectors = 0; for (i = 0; i < crtc_req->count_connectors; i++) { connector_set[i] = NULL; set_connectors_ptr = (uint32_t __user *)(unsigned long)crtc_req->set_connectors_ptr; @@ -871,6 +871,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, connector->name); connector_set[i] = connector; + num_connectors++; } } @@ -879,7 +880,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, set.y = crtc_req->y; set.mode = mode; set.connectors = connector_set; - set.num_connectors = crtc_req->count_connectors; + set.num_connectors = num_connectors; set.fb = fb; if (drm_drv_uses_atomic_modeset(dev)) @@ -892,7 +893,7 @@ out: drm_framebuffer_put(fb); if (connector_set) { - for (i = 0; i < crtc_req->count_connectors; i++) { + for (i = 0; i < num_connectors; i++) { if (connector_set[i]) drm_connector_put(connector_set[i]); } -- 2.7.4