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, 47 insertions, 0 deletions

diff --git a/tools/perf/util/symsrc.h b/tools/perf/util/symsrc.h
new file mode 100644
index 000000000..edf82028c
--- /dev/null
+++ b/tools/perf/util/symsrc.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_SYMSRC_
+#define __PERF_SYMSRC_ 1
+
+#include <stdbool.h>
+#include <stddef.h>
+#include "dso.h"
+
+#ifdef HAVE_LIBELF_SUPPORT
+#include <libelf.h>
+#include <gelf.h>
+#endif
+#include <elf.h>
+
+struct symsrc {
+	char		     *name;
+	int		     fd;
+	enum dso_binary_type type;
+
+#ifdef HAVE_LIBELF_SUPPORT
+	Elf		     *elf;
+	GElf_Ehdr	     ehdr;
+
+	Elf_Scn		     *opdsec;
+	size_t		     opdidx;
+	GElf_Shdr	     opdshdr;
+
+	Elf_Scn		     *symtab;
+	size_t		     symtab_idx;
+	GElf_Shdr	     symshdr;
+
+	Elf_Scn		     *dynsym;
+	size_t		     dynsym_idx;
+	GElf_Shdr	     dynshdr;
+
+	bool		     adjust_symbols;
+	bool		     is_64_bit;
+#endif
+};
+
+int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name, enum dso_binary_type type);
+void symsrc__destroy(struct symsrc *ss);
+
+bool symsrc__has_symtab(struct symsrc *ss);
+bool symsrc__possibly_runtime(struct symsrc *ss);
+
+#endif /* __PERF_SYMSRC_ */