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, 69 insertions, 0 deletions

diff --git a/fs/ubifs/misc.c b/fs/ubifs/misc.c
new file mode 100644
index 000000000..cd23de0f2
--- /dev/null
+++ b/fs/ubifs/misc.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include "ubifs.h"
+
+/* Normal UBIFS messages */
+void ubifs_msg(const struct ubifs_info *c, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	pr_notice("UBIFS (ubi%d:%d): %pV\n",
+		  c->vi.ubi_num, c->vi.vol_id, &vaf);
+
+	va_end(args);
+}								    \
+
+/* UBIFS error messages */
+void ubifs_err(const struct ubifs_info *c, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	pr_err("UBIFS error (ubi%d:%d pid %d): %ps: %pV\n",
+	       c->vi.ubi_num, c->vi.vol_id, current->pid,
+	       __builtin_return_address(0),
+	       &vaf);
+
+	va_end(args);
+}								    \
+
+/* UBIFS warning messages */
+void ubifs_warn(const struct ubifs_info *c, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	pr_warn("UBIFS warning (ubi%d:%d pid %d): %ps: %pV\n",
+		c->vi.ubi_num, c->vi.vol_id, current->pid,
+		__builtin_return_address(0),
+		&vaf);
+
+	va_end(args);
+}
+
+static char *assert_names[] = {
+	[ASSACT_REPORT] = "report",
+	[ASSACT_RO] = "read-only",
+	[ASSACT_PANIC] = "panic",
+};
+
+const char *ubifs_assert_action_name(struct ubifs_info *c)
+{
+	return assert_names[c->assert_action];
+}