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, 45 insertions, 0 deletions

diff --git a/fs/9p/Kconfig b/fs/9p/Kconfig
new file mode 100644
index 000000000..0c63df574
--- /dev/null
+++ b/fs/9p/Kconfig
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config 9P_FS
+	tristate "Plan 9 Resource Sharing Support (9P2000)"
+	depends on NET_9P
+	select NETFS_SUPPORT
+	help
+	  If you say Y here, you will get experimental support for
+	  Plan 9 resource sharing via the 9P2000 protocol.
+
+	  See <http://v9fs.sf.net> for more information.
+
+	  If unsure, say N.
+
+if 9P_FS
+config 9P_FSCACHE
+	bool "Enable 9P client caching support"
+	depends on 9P_FS=m && FSCACHE || 9P_FS=y && FSCACHE=y
+	help
+	  Choose Y here to enable persistent, read-only local
+	  caching support for 9p clients using FS-Cache
+
+
+config 9P_FS_POSIX_ACL
+	bool "9P POSIX Access Control Lists"
+	select FS_POSIX_ACL
+	help
+	  POSIX Access Control Lists (ACLs) support permissions for users and
+	  groups beyond the owner/group/world scheme.
+
+	  If you don't know what Access Control Lists are, say N
+
+endif
+
+
+config 9P_FS_SECURITY
+	bool "9P Security Labels"
+	depends on 9P_FS
+	help
+	  Security labels support alternative access control models
+	  implemented by security modules like SELinux.  This option
+	  enables an extended attribute handler for file security
+	  labels in the 9P filesystem.
+
+	  If you are not using a security module that requires using
+	  extended attributes for file security labels, say N.