From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f69.google.com (mail-oo1-f69.google.com [209.85.161.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 735B913DDAA for ; Tue, 14 Apr 2026 00:16:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.69 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776125794; cv=none; b=OKGLLvoKvJ2YdP4+brftG9TjbQzLKczu/f4+pT5Rm6zSq+VhgoWCf+fFwSnJstHlQd38NDz7ptfGd8j6cIjLPX8XdDbrSyhP/C/Jdf/XRDGxJ8ZGzDcB0zrrq1Y0+cRImljEcWE9rljN/o8Lp84HI1twk/q+aQktr4bXKxizJO8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776125794; c=relaxed/simple; bh=NgMA+w2LES/B+5lCEx8rzzbnCexaq3QvfhIl/e9cNx0=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=RjQcVVe0tnLX9S1UbZPLxLJH8APzCoTkjv+tqFEohnkNddQ5rZQteBX7fuIo6AvnPTdj5WOhBiSkrsVdUY3fuWNJXWvuqyHVgTElkxIYwn9FS8AEuraHyGcjXqmvJzmUL8HA6AKkSrQUe/EqbgT4V4dCLP7FIQLeVXfSk2lwauM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.69 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f69.google.com with SMTP id 006d021491bc7-6853c2438b9so9773226eaf.3 for ; Mon, 13 Apr 2026 17:16:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776125792; x=1776730592; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=SrfF21jLKgspwKBLwt2OgZkZEroGq1ibJuu7wnhyczs=; b=MeScoGWfKXZgXtu4HdQSkUiTrI/WoxyfgA4mQderI/pDR6GgZlAPaAvRPEOcm246Lv ayErznpTxkZB5Uz9Y3N8LOCN2NfkwOAEne1PYFjxHq2/fCv1M9MTWDKbZXYIswG/1XPj S73wrxi4tUjhEZmhrCRy28lm28hAdvAXvY7LQbNhH57Nzd1S46/J3YuduHu7emRucZlC uNBkVEoWuGQG4dJaIgNVfUbtpOjaKcvUssmTFhyXfipfUmMQPbQz3G/BORkTvxPmnoK/ pgQLwoVk7HjfqTOnyYFRUuz8o4J1IXd7eCtYf1xsnsKjVOKJAXeNH1SBtLD3m0EuOfcL pNdA== X-Gm-Message-State: AOJu0Yw3lLsTcPZtLqzVgQOnP63/flC6eLs/ef2jppjEGZO7sr3tBu1j HfMdoAXZeZ/h30ivf1UR6ecVLQwXY7eH2kyc/e+FYzoSn3mEf7moVBf03QHyxbDymY9CLWRxP7K g4UP5XKQEjbQk0fqR/RGvD4tWo7cMHX0EmGTlgap37S10V1F3wbo9PC309ZA= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:f05:b0:680:6d72:9399 with SMTP id 006d021491bc7-68be65304d3mr7789695eaf.24.1776125792461; Mon, 13 Apr 2026 17:16:32 -0700 (PDT) Date: Mon, 13 Apr 2026 17:16:32 -0700 In-Reply-To: <69dd24f4.a00a0220.468cb.004a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69dd8760.a00a0220.468cb.0052.GAE@google.com> Subject: Forwarded: [PATCH] drm/gem: fix use-after-free in drm_gem_release From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] drm/gem: fix use-after-free in drm_gem_release Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master drm_gem_release() calls idr_for_each() with drm_gem_object_release_handle() as callback. A concurrent drm_gem_handle_delete() can free the GEM object between the time idr_for_each() reads the pointer and drm_gem_object_release_handle() uses it, causing a use-after-free. Fix this by splitting the operation into two phases: 1. Under table_lock, walk the IDR using a new collect callback that only increments each object's reference count and adds it to a local list. Only atomic operations are performed here so holding a spinlock is safe. 2. Outside the lock, iterate the local list and call drm_gem_object_release_handle() on each object safely. Drop our reference afterwards and destroy the IDR only after all objects have been properly released. Holding a reference during phase 1 ensures that a concurrent drm_gem_handle_delete() cannot free any object while we are still using it. Reported-by: syzbot+b2e951687503f32f74ce@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b2e951687503f32f74ce Signed-off-by: Deepanshu Kartikey --- drivers/gpu/drm/drm_gem.c | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 891c3bff5ae0..ee9939356de4 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1073,6 +1073,30 @@ drm_gem_open(struct drm_device *dev, struct drm_file *file_private) spin_lock_init(&file_private->table_lock); } +struct drm_gem_object_entry { + struct drm_gem_object *obj; + struct list_head head; +}; + +static int drm_gem_object_collect(int id, void *ptr, void *data) +{ + struct drm_gem_object_entry *entry; + struct drm_gem_object *obj = ptr; + struct list_head *list = data; + + if (!obj) + return 0; + + entry = kmalloc_obj(*entry, GFP_ATOMIC); + if (!entry) + return -ENOMEM; + + drm_gem_object_get(obj); + entry->obj = obj; + list_add(&entry->head, list); + return 0; +} + /** * drm_gem_release - release file-private GEM resources * @dev: drm_device which is being closed by userspace @@ -1085,8 +1109,21 @@ drm_gem_open(struct drm_device *dev, struct drm_file *file_private) void drm_gem_release(struct drm_device *dev, struct drm_file *file_private) { + struct drm_gem_object_entry *entry, *tmp; + LIST_HEAD(list); + + spin_lock(&file_private->table_lock); idr_for_each(&file_private->object_idr, - &drm_gem_object_release_handle, file_private); + &drm_gem_object_collect, &list); + spin_unlock(&file_private->table_lock); + + list_for_each_entry_safe(entry, tmp, &list, head) { + list_del(&entry->head); + drm_gem_object_release_handle(0, entry->obj, file_private); + drm_gem_object_put(entry->obj); + kfree(entry); + } + idr_destroy(&file_private->object_idr); } -- 2.43.0