xfs: Fix bulkstat compat ioctls on x32 userspace.

The bulkstat family of ioctls are problematic on x32, because there is
a mixup of native 32-bit and 64-bit conventions.  The xfs_fsop_bulkreq
struct contains pointers and 32-bit integers so that matches the native
32-bit layout, and that means the ioctl implementation goes into the
regular compat path on x32.

However, the 'ubuffer' member of that struct in turn refers to either
struct xfs_inogrp or xfs_bstat (or an array of these).  On x32, those
structures match the native 64-bit layout.  The compat implementation
writes out the 32-bit version of these structures.  This is not the
expected format for x32 userspace, causing problems.

Fortunately the functions which actually output these xfs_inogrp and
xfs_bstat structures have an easy way to select which output format
is required, so we just need a little tweak to select the right format
on x32.

Signed-off-by: Nick Bowler <nbowler@draconx.ca>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 30 insertions, 4 deletions

diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
index 4c34efcbf7e8..b044f7d36782 100644
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -241,6 +241,32 @@ xfs_compat_ioc_bulkstat(
 	int			done;
 	int			error;
 
+	/*
+	 * Output structure handling functions.  Depending on the command,
+	 * either the xfs_bstat and xfs_inogrp structures are written out
+	 * to userpace memory via bulkreq.ubuffer.  Normally the compat
+	 * functions and structure size are the correct ones to use ...
+	 */
+	inumbers_fmt_pf inumbers_func = xfs_inumbers_fmt_compat;
+	bulkstat_one_pf	bs_one_func = xfs_bulkstat_one_compat;
+	size_t bs_one_size = sizeof(struct compat_xfs_bstat);
+
+#ifdef CONFIG_X86_X32
+	if (in_x32_syscall()) {
+		/*
+		 * ... but on x32 the input xfs_fsop_bulkreq has pointers
+		 * which must be handled in the "compat" (32-bit) way, while
+		 * the xfs_bstat and xfs_inogrp structures follow native 64-
+		 * bit layout convention.  So adjust accordingly, otherwise
+		 * the data written out in compat layout will not match what
+		 * x32 userspace expects.
+		 */
+		inumbers_func = xfs_inumbers_fmt;
+		bs_one_func = xfs_bulkstat_one;
+		bs_one_size = sizeof(struct xfs_bstat);
+	}
+#endif
+
 	/* done = 1 if there are more stats to get and if bulkstat */
 	/* should be called again (unused here, but used in dmapi) */
 
@@ -272,15 +298,15 @@ xfs_compat_ioc_bulkstat(
 
 	if (cmd == XFS_IOC_FSINUMBERS_32) {
 		error = xfs_inumbers(mp, &inlast, &count,
-				bulkreq.ubuffer, xfs_inumbers_fmt_compat);
+				bulkreq.ubuffer, inumbers_func);
 	} else if (cmd == XFS_IOC_FSBULKSTAT_SINGLE_32) {
 		int res;
 
-		error = xfs_bulkstat_one_compat(mp, inlast, bulkreq.ubuffer,
-				sizeof(compat_xfs_bstat_t), NULL, &res);
+		error = bs_one_func(mp, inlast, bulkreq.ubuffer,
+				bs_one_size, NULL, &res);
 	} else if (cmd == XFS_IOC_FSBULKSTAT_32) {
 		error = xfs_bulkstat(mp, &inlast, &count,
-			xfs_bulkstat_one_compat, sizeof(compat_xfs_bstat_t),
+			bs_one_func, bs_one_size,
 			bulkreq.ubuffer, &done);
 	} else
 		error = -EINVAL;