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, 41 insertions, 0 deletions

diff --git a/include/drm/intel/intel-gtt.h b/include/drm/intel/intel-gtt.h
new file mode 100644
index 000000000..f53bcff01
--- /dev/null
+++ b/include/drm/intel/intel-gtt.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Common header for intel-gtt.ko and i915.ko */
+
+#ifndef _DRM_INTEL_GTT_H
+#define	_DRM_INTEL_GTT_H
+
+#include <linux/types.h>
+
+struct agp_bridge_data;
+struct pci_dev;
+struct sg_table;
+
+void intel_gmch_gtt_get(u64 *gtt_total,
+			phys_addr_t *mappable_base,
+			resource_size_t *mappable_end);
+
+int intel_gmch_probe(struct pci_dev *bridge_pdev, struct pci_dev *gpu_pdev,
+		     struct agp_bridge_data *bridge);
+void intel_gmch_remove(void);
+
+bool intel_gmch_enable_gtt(void);
+
+void intel_gmch_gtt_flush(void);
+void intel_gmch_gtt_insert_page(dma_addr_t addr,
+				unsigned int pg,
+				unsigned int flags);
+void intel_gmch_gtt_insert_sg_entries(struct sg_table *st,
+				      unsigned int pg_start,
+				      unsigned int flags);
+void intel_gmch_gtt_clear_range(unsigned int first_entry, unsigned int num_entries);
+dma_addr_t intel_gmch_gtt_read_entry(unsigned int pg,
+				     bool *is_present, bool *is_local);
+
+/* Special gtt memory types */
+#define AGP_DCACHE_MEMORY	1
+#define AGP_PHYS_MEMORY		2
+
+/* flag for GFDT type */
+#define AGP_USER_CACHED_MEMORY_GFDT (1 << 3)
+
+#endif