openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 103 insertions, 0 deletions

diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
new file mode 100644
index 000000000..95050e719
--- /dev/null
+++ b/fs/gfs2/dentry.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <linux/gfs2_ondisk.h>
+#include <linux/namei.h>
+#include <linux/crc32.h>
+
+#include "gfs2.h"
+#include "incore.h"
+#include "dir.h"
+#include "glock.h"
+#include "super.h"
+#include "util.h"
+#include "inode.h"
+
+/**
+ * gfs2_drevalidate - Check directory lookup consistency
+ * @dir: expected parent directory inode
+ * @name: expexted name
+ * @dentry: dentry to check
+ * @flags: lookup flags
+ *
+ * Check to make sure the lookup necessary to arrive at this inode from its
+ * parent is still good.
+ *
+ * Returns: 1 if the dentry is ok, 0 if it isn't
+ */
+
+static int gfs2_drevalidate(struct inode *dir, const struct qstr *name,
+			    struct dentry *dentry, unsigned int flags)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(dir);
+	struct gfs2_inode *dip = GFS2_I(dir);
+	struct inode *inode;
+	struct gfs2_holder d_gh;
+	struct gfs2_inode *ip = NULL;
+	int error, valid;
+	int had_lock = 0;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = d_inode(dentry);
+
+	if (inode) {
+		if (is_bad_inode(inode))
+			return 0;
+		ip = GFS2_I(inode);
+	}
+
+	if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL)
+		return 1;
+
+	had_lock = (gfs2_glock_is_locked_by_me(dip->i_gl) != NULL);
+	if (!had_lock) {
+		error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
+		if (error)
+			return 0;
+	}
+
+	error = gfs2_dir_check(dir, name, ip);
+	valid = inode ? !error : (error == -ENOENT);
+
+	if (!had_lock)
+		gfs2_glock_dq_uninit(&d_gh);
+	return valid;
+}
+
+static int gfs2_dhash(const struct dentry *dentry, struct qstr *str)
+{
+	str->hash = gfs2_disk_hash(str->name, str->len);
+	return 0;
+}
+
+static int gfs2_dentry_delete(const struct dentry *dentry)
+{
+	struct gfs2_inode *ginode;
+
+	if (d_really_is_negative(dentry))
+		return 0;
+
+	ginode = GFS2_I(d_inode(dentry));
+	if (!gfs2_holder_initialized(&ginode->i_iopen_gh))
+		return 0;
+
+	if (test_bit(GLF_DEMOTE, &ginode->i_iopen_gh.gh_gl->gl_flags))
+		return 1;
+
+	return 0;
+}
+
+const struct dentry_operations gfs2_dops = {
+	.d_revalidate = gfs2_drevalidate,
+	.d_hash = gfs2_dhash,
+	.d_delete = gfs2_dentry_delete,
+};
+