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, 34 insertions, 0 deletions

diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
new file mode 100644
index 000000000..e66e13e79
--- /dev/null
+++ b/scripts/Makefile.btf
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0
+
+pahole-ver := $(CONFIG_PAHOLE_VERSION)
+pahole-flags-y :=
+
+JOBS := $(patsubst -j%,%,$(filter -j%,$(MAKEFLAGS)))
+
+ifeq ($(call test-le, $(pahole-ver), 125),y)
+
+pahole-flags-y                                  	+= --btf_gen_floats -j$(JOBS)
+
+pahole-flags-$(call test-ge, $(pahole-ver), 125)	+= --skip_encoding_btf_inconsistent_proto --btf_gen_optimized
+
+else
+
+# Switch to using --btf_features for v1.26 and later.
+pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j$(JOBS) --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func,decl_tag_kfuncs
+
+pahole-flags-$(call test-ge, $(pahole-ver), 130) += --btf_features=attributes
+
+pahole-flags-$(call test-ge, $(pahole-ver), 131) += --btf_features=layout
+
+endif
+
+pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE)		+= --lang_exclude=rust
+
+export PAHOLE_FLAGS := $(pahole-flags-y)
+
+resolve-btfids-flags-y :=
+resolve-btfids-flags-$(CONFIG_WERROR) += --fatal_warnings
+resolve-btfids-flags-$(if $(KBUILD_EXTMOD),y) += --distill_base
+resolve-btfids-flags-$(if $(KBUILD_VERBOSE),y) += --verbose
+
+export RESOLVE_BTFIDS_FLAGS := $(resolve-btfids-flags-y)