From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792773985; b=s4pOd7QkJRYzg5UWjtFumoSzXvTa7QlPBrMR+kI9CamVc9gxFhp0KtlOuzmWhUMAfDM3 kNIPUS+ujON5OrVqIri7As6LmX30w54BbTvmbJQEKlLFM3sjVTU8FDHCXwqqDm/5kuTi8 ZKzVNi+WzLKYYSYztIU1T3Obv+x/37IHlKh/Ev8du3vqBbSvPxU9eXf0rkhL1+4MnNkw/ LG/Obn+2B/9njhn+uhB7co4iUnYOifBaKSA2DfV3CXabfGgQLyrGgEJhthPY+W9BgQuw0 AZ1W07HgsBtmC9nP9WofNo0CipsoCJfkcrY2rqI3oZZylA2TRe/MtmhMoYoHor3zxMA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792773985; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=NWmqOswqMZF++VNuODD05e1aIvNjLVxmdzwDlYKMRPM=; b=zpZYxLNqmTwtVs19Tqvq2y60AjbhnYJ69gyQJEFuCVN8kRr5ciEG78N2JDAST/JAaFbH jJLAbKd4grrebukHI0hUX/VRU3XR99CEdYRqjh/kGCyjhEcYpckpYNZ0+Z4b7Ww2OsIj5 QXg/Jf8OiqzPatv6mUoWcxxJmLVjxSY2k6wlEQ1AbFmp8IG0W6ON8yJF7eaX3DvYkMEYk Q0S2Pw252OThH1cjBE7jWb6FOYBwJnPS3xpqN8EcLcl2DuQOhpleroiG2DtsyFE6XcTBP eG0XJop2bs0wgtkNuTM/HIO5kLo73jAElgO8U1hAmEJtFr/fPj7P/gT+qLiwIrQRu4Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=mZQwPbYm; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A2B98606A31D; Fri, 23 Oct 2026 16:46:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=mZQwPbYm Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0CFC1F01825; Fri, 23 Oct 2026 16:46:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792773985; bh=NWmqOswqMZF++VNuODD05e1aIvNjLVxmdzwDlYKMRPM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mZQwPbYmKM72G9ewQKeMjFOLq0CilPhjO1h1pdTZaV4yQb5lr5Six4A/rCw791l0c 7AUjBHPdxBHpw0MuAull3M6NQGrdnp3SCgNm4GRTSYXeekRYTirXTZWQ1LTh9sxCMt 7ab6gGYvajFDhuA27djbeKAAvwZrBginpEy2uXtE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kyle Zeng , "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.18 055/193] pipe: preserve existing fasync readers on writer setup failure Date: Fri, 23 Oct 2026 18:35:32 +0200 Message-ID: <20261023163715.507313789@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163714.201276352@linuxfoundation.org> References: <20261023163714.201276352@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kyle Zeng [ Upstream commit 40bb03d3ea6f6a915218508819ecc4d7a7fa260d ] F_SETFL and FIOASYNC decide whether to invoke ->fasync() before pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can therefore both enter the callback. fasync_helper() allocates before checking for an existing entry. If the first enable installs both entries, a second enable can update the reader entry and then fail the allocation for the writer entry. The error path removes the pre-existing reader entry, clearing FASYNC while the writer entry remains registered. __fput() then skips ->fasync(), so a later pipe notification can dereference the freed file or its f_owner. An unprivileged memory-pressure reproducer triggers a KASAN slab-use-after-free in send_sigio() through this path. Keep the reader helper's result and undo the registration only if this call added it. The pipe mutex serializes changes to both lists, so a failed new registration still removes its reader, while a failed duplicate preserves the existing registrations and FASYNC. Successful duplicate enables continue to update fa_fd as before. Fixes: 76398425bb06 ("Move FASYNC bit handling to f_op->fasync()") Signed-off-by: Kyle Zeng Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin --- fs/pipe.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 42fead1efe520..ec1742bad3e79 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -755,9 +755,11 @@ pipe_fasync(int fd, struct file *filp, int on) if (filp->f_mode & FMODE_READ) retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); if ((filp->f_mode & FMODE_WRITE) && retval >= 0) { + int read_ret = retval; + retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); - if (retval < 0 && (filp->f_mode & FMODE_READ)) - /* this can happen only if on == T */ + /* Undo only a reader entry added by this call. */ + if (retval < 0 && read_ret > 0) fasync_helper(-1, filp, 0, &pipe->fasync_readers); } mutex_unlock(&pipe->mutex); -- 2.53.0