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, 28 insertions, 0 deletions

diff --git a/net/dns_resolver/Kconfig b/net/dns_resolver/Kconfig
new file mode 100644
index 000000000..7c2dba273
--- /dev/null
+++ b/net/dns_resolver/Kconfig
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Configuration for DNS Resolver
+#
+config DNS_RESOLVER
+	tristate "DNS Resolver support"
+	depends on KEYS
+	help
+	  Saying Y here will include support for the DNS Resolver key type
+	  which can be used to make upcalls to perform DNS lookups in
+	  userspace.
+
+	  DNS Resolver is used to query DNS server for information.  Examples
+	  being resolving a UNC hostname element to an IP address for CIFS or
+	  performing a DNS query for AFSDB records so that AFS can locate a
+	  cell's volume location database servers.
+
+	  DNS Resolver is used by the CIFS and AFS modules, and would support
+	  SMB2 later.  DNS Resolver is supported by the userspace upcall
+	  helper "/sbin/dns.resolver" via /etc/request-key.conf.
+
+	  See <file:Documentation/networking/dns_resolver.rst> for further
+	  information.
+
+	  To compile this as a module, choose M here: the module will be called
+	  dns_resolver.
+
+	  If unsure, say N.