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 <a...@arndb.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

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