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, 35 insertions, 0 deletions

diff --git a/crypto/jitterentropy.h b/crypto/jitterentropy.h
new file mode 100644
index 000000000..5bb15cb33
--- /dev/null
+++ b/crypto/jitterentropy.h
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+struct sha3_ctx;
+extern void *jent_kvzalloc(unsigned int len);
+extern void jent_kvzfree(void *ptr, unsigned int len);
+extern void *jent_zalloc(unsigned int len);
+extern void jent_zfree(void *ptr);
+extern void jent_get_nstime(__u64 *out);
+void jent_hash_time(struct sha3_ctx *hash_state, __u64 time, u8 *addtl,
+		    unsigned int addtl_len, __u64 hash_loop_cnt,
+		    unsigned int stuck);
+void jent_read_random_block(struct sha3_ctx *hash_state, char *dst,
+			    unsigned int dst_len);
+
+struct rand_data;
+extern int jent_entropy_init(unsigned int osr, unsigned int flags,
+			     struct sha3_ctx *hash_state,
+			     struct rand_data *p_ec);
+extern int jent_read_entropy(struct rand_data *ec, unsigned char *data,
+			     unsigned int len);
+
+extern struct rand_data *
+jent_entropy_collector_alloc(unsigned int osr, unsigned int flags,
+			     struct sha3_ctx *hash_state);
+extern void jent_entropy_collector_free(struct rand_data *entropy_collector);
+
+#ifdef CONFIG_CRYPTO_JITTERENTROPY_TESTINTERFACE
+int jent_raw_hires_entropy_store(__u64 value);
+void jent_testing_init(void);
+void jent_testing_exit(void);
+#else /* CONFIG_CRYPTO_JITTERENTROPY_TESTINTERFACE */
+static inline int jent_raw_hires_entropy_store(__u64 value) { return 0; }
+static inline void jent_testing_init(void) { }
+static inline void jent_testing_exit(void) { }
+#endif /* CONFIG_CRYPTO_JITTERENTROPY_TESTINTERFACE */