From: Zack Rusin Date: Tue, 5 May 2026 22:22:25 +0000 (-0400) Subject: drm/vmwgfx: take fman->lock around fence list mutation in fifo_down X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=250af2e8c3e90dc978e062a936b633870a22e660;p=thirdparty%2Flinux.git drm/vmwgfx: take fman->lock around fence list mutation in fifo_down vmw_fence_fifo_down() drops fman->lock to wait on a fence and, on timeout, mutates fman->fence_list via list_del_init() and signals the fence without re-acquiring the lock. __vmw_fences_update() walks and removes entries from the same list under fman->lock from any other waiter, the fence-IRQ thread, or vmw_fences_update(), so the unlocked list_del_init() can corrupt the list head. Re-take fman->lock before manipulating fence->head and use dma_fence_signal_locked(). Wrap the locked signalling in dma_fence_begin_signalling() / dma_fence_end_signalling() so the lockdep annotation that dma_fence_signal() previously provided is preserved (the same pattern as __vmw_fences_update()). dma_fence_put() is moved outside the lock to avoid a recursive acquire from vmw_fence_obj_destroy(), which also takes fman->lock. Fixes: ae2a104058e2 ("vmwgfx: Implement fence objects") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4.7 Signed-off-by: Zack Rusin Reviewed-by: Ian Forbes Link: https://patch.msgid.link/20260505222728.519626-5-zack.rusin@broadcom.com --- diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c index 4ef84ff9b638..384c6736cf6b 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c @@ -367,13 +367,24 @@ void vmw_fence_fifo_down(struct vmw_fence_manager *fman) ret = vmw_fence_obj_wait(fence, false, false, VMW_FENCE_WAIT_TIMEOUT); + spin_lock(&fman->lock); if (unlikely(ret != 0)) { + bool cookie = dma_fence_begin_signalling(); + list_del_init(&fence->head); - dma_fence_signal(&fence->base); + if (fence->waiter_added) { + vmw_seqno_waiter_remove(fman->dev_priv); + fence->waiter_added = false; + } + dma_fence_signal_locked(&fence->base); + dma_fence_end_signalling(cookie); } BUG_ON(!list_empty(&fence->head)); + spin_unlock(&fman->lock); + dma_fence_put(&fence->base); + spin_lock(&fman->lock); } spin_unlock(&fman->lock);