From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1DD78149C51; Fri, 6 Dec 2024 15:25:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733498754; cv=none; b=VpH93WeVj4re3H1CTdObOtClE6Mu/ok9pDFE2jJM3z/QQp3upnTwvjnf93m8+1B2m5LBXr7sqM99zIG5oBBDYejg54c8F/c4//ac7wVbvOxyN89BLcaDt22TgnGs5ScQDxWXkD+FqFuqUNVw+z6GKgB6gKN7zGwY0H8TMwnU15s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733498754; c=relaxed/simple; bh=FG8Ap0c1EEcM7SpEydFYpGWYOSzBmEyJw0O+05CtlIc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gtCzYG6hc/Hdq9baVPapVJETNJW1ECQpSmBv6GnYArF6FciE1BW/0OAoVCKOLkdBTD9A8lNuamJUaWRDvHlvfZ5Ya1nlqC4xLDCO50f1TFyiDTGVpMWTth0iEZ27suA6PyTFLiANcD8OFiqHGGcMTmIj/FFg6aEkm879df4JYfY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hzaxjEck; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hzaxjEck" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 825E7C4CEDC; Fri, 6 Dec 2024 15:25:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733498754; bh=FG8Ap0c1EEcM7SpEydFYpGWYOSzBmEyJw0O+05CtlIc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hzaxjEck7b4QhZ4KYJipHobhJ525M8eQPzMXFc2NUAbSrAPEkLT81og6SaiHV0qYp yWsIviHHq9VWY1bTPq/XdINdfds4Mtb8+RErvhLQxJrvfltij2cFLUWPBghGhSAGJN ulYFzsLgISF6luSxDRcnwjSLOnbAO9DLpiV/ByWA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yang Erkun , Jeff Layton , Chuck Lever Subject: [PATCH 6.6 656/676] nfsd: make sure exp active before svc_export_show Date: Fri, 6 Dec 2024 15:37:55 +0100 Message-ID: <20241206143718.991803222@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241206143653.344873888@linuxfoundation.org> References: <20241206143653.344873888@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yang Erkun commit be8f982c369c965faffa198b46060f8853e0f1f0 upstream. The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active. ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 819 at lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Call Trace: e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: bf18f163e89c ("NFSD: Using exp_get for export getting") Cc: stable@vger.kernel.org # 4.20+ Signed-off-by: Yang Erkun Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/export.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -1385,9 +1385,12 @@ static int e_show(struct seq_file *m, vo return 0; } - exp_get(exp); + if (!cache_get_rcu(&exp->h)) + return 0; + if (cache_check(cd, &exp->h, NULL)) return 0; + exp_put(exp); return svc_export_show(m, cd, cp); }