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, 44 insertions, 0 deletions

diff --git a/fs/overlayfs/params.h b/fs/overlayfs/params.h
new file mode 100644
index 000000000..ffd53cdd8
--- /dev/null
+++ b/fs/overlayfs/params.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+
+struct ovl_fs;
+struct ovl_config;
+
+extern const struct fs_parameter_spec ovl_parameter_spec[];
+extern const struct constant_table ovl_parameter_redirect_dir[];
+
+/* The set of options that user requested explicitly via mount options */
+struct ovl_opt_set {
+	bool metacopy;
+	bool redirect;
+	bool nfs_export;
+	bool index;
+};
+
+#define OVL_MAX_STACK 500
+
+struct ovl_fs_context_layer {
+	char *name;
+	struct path path;
+};
+
+struct ovl_fs_context {
+	struct path upper;
+	struct path work;
+	size_t capacity;
+	size_t nr; /* includes nr_data */
+	size_t nr_data;
+	struct ovl_opt_set set;
+	struct ovl_fs_context_layer *lower;
+	char *lowerdir_all; /* user provided lowerdir string */
+	bool casefold_set;
+};
+
+int ovl_init_fs_context(struct fs_context *fc);
+void ovl_free_fs(struct ovl_fs *ofs);
+int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
+			 struct ovl_config *config);
+int ovl_show_options(struct seq_file *m, struct dentry *dentry);
+const char *ovl_xino_mode(struct ovl_config *config);