linux-kernel - [PATCH 2/3] xfs: disallow broken ioctls without compat-32-bit-time

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Message-Id: <20191218163954.296726-2-arnd@arndb.de>
Date:   Wed, 18 Dec 2019 17:39:29 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org
Cc:     y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
        Brian Foster <bfoster@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        Allison Collins <allison.henderson@...cle.com>,
        Jan Kara <jack@...e.cz>, Eric Sandeen <sandeen@...deen.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] xfs: disallow broken ioctls without compat-32-bit-time

When building a kernel that disables support for 32-bit time_t
system calls, it also makes sense to disable the old xfs_bstat
ioctls completely, as they truncate the timestamps to 32-bit
values once the extended times are supported.

Any application using these needs to be updated to use the v5
interfaces.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/xfs/xfs_ioctl.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 7b35d62ede9f..d43582e933a0 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -36,6 +36,7 @@
 #include "xfs_reflink.h"
 #include "xfs_ioctl.h"
 
+#include <linux/compat.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
 
@@ -617,6 +618,23 @@ xfs_fsinumbers_fmt(
 	return xfs_ibulk_advance(breq, sizeof(struct xfs_inogrp));
 }
 
+/* disallow y2038-unsafe ioctls with CONFIG_COMPAT_32BIT_TIME=n */
+static bool xfs_have_compat_bstat_time32(unsigned int cmd)
+{
+	if (IS_ENABLED(CONFIG_COMPAT_32BIT_TIME))
+		return true;
+
+	if (IS_ENABLED(CONFIG_64BIT) && !in_compat_syscall())
+		return true;
+
+	if (cmd == XFS_IOC_FSBULKSTAT_SINGLE ||
+	    cmd == XFS_IOC_FSBULKSTAT ||
+	    cmd == XFS_IOC_SWAPEXT)
+		return false;
+
+	return true;
+}
+
 STATIC int
 xfs_ioc_fsbulkstat(
 	xfs_mount_t		*mp,
@@ -637,6 +655,9 @@ xfs_ioc_fsbulkstat(
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (!xfs_have_compat_bstat_time32(cmd))
+		return -EINVAL;
+
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return -EIO;
 
@@ -1815,6 +1836,11 @@ xfs_ioc_swapext(
 	struct fd	f, tmp;
 	int		error = 0;
 
+	if (!xfs_have_compat_bstat_time32(XFS_IOC_SWAPEXT)) {
+		error = -EINVAL;
+		goto out;
+	}
+
 	/* Pull information for the target fd */
 	f = fdget((int)sxp->sx_fdtarget);
 	if (!f.file) {
-- 
2.20.0