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, 150 insertions, 0 deletions

diff --git a/fs/befs/befs.h b/fs/befs/befs.h
new file mode 100644
index 000000000..7cd472456
--- /dev/null
+++ b/fs/befs/befs.h
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * befs.h
+ *
+ * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
+ * Copyright (C) 1999 Makoto Kato (m_kato@ga2.so-net.ne.jp)
+ */
+
+#ifndef _LINUX_BEFS_H
+#define _LINUX_BEFS_H
+
+#include "befs_fs_types.h"
+
+/* used in debug.c */
+#define BEFS_VERSION "0.9.3"
+
+
+typedef u64 befs_blocknr_t;
+/*
+ * BeFS in memory structures
+ */
+
+struct befs_mount_options {
+	kgid_t gid;
+	kuid_t uid;
+	int use_gid;
+	int use_uid;
+	int debug;
+	char *iocharset;
+};
+
+struct befs_sb_info {
+	u32 magic1;
+	u32 block_size;
+	u32 block_shift;
+	int byte_order;
+	befs_off_t num_blocks;
+	befs_off_t used_blocks;
+	u32 inode_size;
+	u32 magic2;
+
+	/* Allocation group information */
+	u32 blocks_per_ag;
+	u32 ag_shift;
+	u32 num_ags;
+
+	/* State of the superblock */
+	u32 flags;
+
+	/* Journal log entry */
+	befs_block_run log_blocks;
+	befs_off_t log_start;
+	befs_off_t log_end;
+
+	befs_inode_addr root_dir;
+	befs_inode_addr indices;
+	u32 magic3;
+
+	struct befs_mount_options mount_opts;
+	struct nls_table *nls;
+};
+
+struct befs_inode_info {
+	u32 i_flags;
+	u32 i_type;
+
+	befs_inode_addr i_inode_num;
+	befs_inode_addr i_parent;
+	befs_inode_addr i_attribute;
+
+	union {
+		befs_data_stream ds;
+		char symlink[BEFS_SYMLINK_LEN];
+	} i_data;
+
+	struct inode vfs_inode;
+};
+
+enum befs_err {
+	BEFS_OK,
+	BEFS_ERR,
+	BEFS_BAD_INODE,
+	BEFS_BT_END,
+	BEFS_BT_EMPTY,
+	BEFS_BT_MATCH,
+	BEFS_BT_OVERFLOW,
+	BEFS_BT_NOT_FOUND
+};
+
+
+/****************************/
+/* debug.c */
+__printf(2, 3)
+void befs_error(const struct super_block *sb, const char *fmt, ...);
+__printf(2, 3)
+void befs_warning(const struct super_block *sb, const char *fmt, ...);
+__printf(2, 3)
+void befs_debug(const struct super_block *sb, const char *fmt, ...);
+
+void befs_dump_super_block(const struct super_block *sb, befs_super_block *);
+void befs_dump_inode(const struct super_block *sb, befs_inode *);
+void befs_dump_index_entry(const struct super_block *sb, befs_disk_btree_super *);
+void befs_dump_index_node(const struct super_block *sb, befs_btree_nodehead *);
+/****************************/
+
+
+/* Gets a pointer to the private portion of the super_block
+ * structure from the public part
+ */
+static inline struct befs_sb_info *
+BEFS_SB(const struct super_block *super)
+{
+	return (struct befs_sb_info *) super->s_fs_info;
+}
+
+static inline struct befs_inode_info *
+BEFS_I(const struct inode *inode)
+{
+	return container_of(inode, struct befs_inode_info, vfs_inode);
+}
+
+static inline befs_blocknr_t
+iaddr2blockno(struct super_block *sb, const befs_inode_addr *iaddr)
+{
+	return ((iaddr->allocation_group << BEFS_SB(sb)->ag_shift) +
+		iaddr->start);
+}
+
+static inline befs_inode_addr
+blockno2iaddr(struct super_block *sb, befs_blocknr_t blockno)
+{
+	befs_inode_addr iaddr;
+
+	iaddr.allocation_group = blockno >> BEFS_SB(sb)->ag_shift;
+	iaddr.start =
+	    blockno - (iaddr.allocation_group << BEFS_SB(sb)->ag_shift);
+	iaddr.len = 1;
+
+	return iaddr;
+}
+
+static inline unsigned int
+befs_iaddrs_per_block(struct super_block *sb)
+{
+	return BEFS_SB(sb)->block_size / sizeof(befs_disk_inode_addr);
+}
+
+#include "endian.h"
+
+#endif				/* _LINUX_BEFS_H */