From patchwork Tue Apr 23 19:13:10 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dmitry Antipov X-Patchwork-Id: 791370 Received: from forward204c.mail.yandex.net (forward204c.mail.yandex.net [178.154.239.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ADE7313FD9E for ; Tue, 23 Apr 2024 19:21:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.154.239.217 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713900093; cv=none; b=nSvWPj5gabUylVNwWmLUSOldIF2X6SLDQGXYstXSryJg/Z0VSCnPYM9Mx0AB62vIq7Or7NIbtFIkjaE7iX30sbBXwrD9jKsBvhdfCPmzXTUc4uurIqV3gqj/hOGGVR1hfCVr5PpTuFvctWRIQ9kOiMOIjNkSotaBn05GA1jLIfw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713900093; c=relaxed/simple; bh=kjvhhljX2lPQ078qSyN97XGReivHZEDzVYujybo01GU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=uyo4CrzgFPLmW/KeK7G/c9mAQP6H3JTmj1VLRZFVbRMiPQmDQ6g5l7O+BZN+cELJ9TBKs7umZAq8/5qMqLflEaJD4ozCFrw6lU0c/iQMejYz+DeUMQxA0LMHa5rmbp6f/W+Fb6k3ASyDuBLYygczYXN6qBUl/Lz4WXuX2N1Fy/U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yandex.ru; spf=pass smtp.mailfrom=yandex.ru; dkim=pass (1024-bit key) header.d=yandex.ru header.i=@yandex.ru header.b=bzDQ0x6Z; arc=none smtp.client-ip=178.154.239.217 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yandex.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=yandex.ru Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=yandex.ru header.i=@yandex.ru header.b="bzDQ0x6Z" Received: from forward103c.mail.yandex.net (forward103c.mail.yandex.net [IPv6:2a02:6b8:c03:500:1:45:d181:d103]) by forward204c.mail.yandex.net (Yandex) with ESMTPS id 05F5561AA8 for ; Tue, 23 Apr 2024 22:13:46 +0300 (MSK) Received: from mail-nwsmtp-smtp-production-main-63.sas.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-63.sas.yp-c.yandex.net [IPv6:2a02:6b8:c08:1699:0:640:fad2:0]) by forward103c.mail.yandex.net (Yandex) with ESMTPS id 1AE3C608F2; Tue, 23 Apr 2024 22:13:38 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-63.sas.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id aDQ1Y2KV04Y0-2XDCZw09; Tue, 23 Apr 2024 22:13:37 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1713899617; bh=m8rHljVzEMT49ON9+udmCkXCxIYBV78xM53MloEwSVg=; h=Message-ID:Date:Cc:Subject:To:From; b=bzDQ0x6ZF12N0ud7Slsp9GrH9ITSqPAo2r2k+XXWXExf++djG65wpSwIgDjo1w6zy jACK33lfOLEIeG2SSK7GTiRGaClpZRgLCwNs2KzvmHTobV8vdVmCEtFGdg+rW03be4 /88zq9IR+dyqpHpxNc03SGG6eo+Q5QXcDZFKdOfU= Authentication-Results: mail-nwsmtp-smtp-production-main-63.sas.yp-c.yandex.net; dkim=pass header.i=@yandex.ru From: Dmitry Antipov To: Sumit Semwal , =?utf-8?q?Christian_K=C3=B6nig?= Cc: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, lvc-project@linuxtesting.org, Dmitry Antipov , syzbot+5d4cb6b4409edfd18646@syzkaller.appspotmail.com Subject: [PATCH] [RFC] dma-buf: fix race condition between poll and close Date: Tue, 23 Apr 2024 22:13:10 +0300 Message-ID: <20240423191310.19437-1-dmantipov@yandex.ru> X-Mailer: git-send-email 2.44.0 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Syzbot has found the race condition where 'fput()' is in progress when 'dma_buf_poll()' makes an attempt to hold the 'struct file' with zero 'f_count'. So use explicit 'atomic_long_inc_not_zero()' to detect such a case and cancel an undergoing poll activity with EPOLLERR. Reported-by: syzbot+5d4cb6b4409edfd18646@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5d4cb6b4409edfd18646 Signed-off-by: Dmitry Antipov Reported-by: syzbot+5d4cb6b4409edfd18646@syzkaller.appspotmail.com Tested-by: Dmitry Antipov --- drivers/dma-buf/dma-buf.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 8fe5aa67b167..39eb75d23219 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -266,8 +266,17 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) spin_unlock_irq(&dmabuf->poll.lock); if (events & EPOLLOUT) { - /* Paired with fput in dma_buf_poll_cb */ - get_file(dmabuf->file); + /* + * Catch the case when fput() is in progress + * (e.g. due to close() from another thread). + * Otherwise the paired fput() will be issued + * from dma_buf_poll_cb(). + */ + if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) { + events = EPOLLERR; + dcb->active = 0; + goto out; + } if (!dma_buf_poll_add_cb(resv, true, dcb)) /* No callback queued, wake up any other waiters */ @@ -289,8 +298,12 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) spin_unlock_irq(&dmabuf->poll.lock); if (events & EPOLLIN) { - /* Paired with fput in dma_buf_poll_cb */ - get_file(dmabuf->file); + /* See above */ + if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) { + events = EPOLLERR; + dcb->active = 0; + goto out; + } if (!dma_buf_poll_add_cb(resv, false, dcb)) /* No callback queued, wake up any other waiters */ @@ -299,7 +312,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) events &= ~EPOLLIN; } } - +out: dma_resv_unlock(resv); return events; }