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, 44 insertions, 0 deletions

diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
new file mode 100644
index 000000000..682bd8ec2
--- /dev/null
+++ b/fs/afs/Kconfig
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config AFS_FS
+	tristate "Andrew File System support (AFS)"
+	depends on INET
+	select AF_RXRPC
+	select DNS_RESOLVER
+	select NETFS_SUPPORT
+	select CRYPTO_KRB5
+	help
+	  If you say Y here, you will get an experimental Andrew File System
+	  driver. It currently only supports unsecured read-only AFS access.
+
+	  See <file:Documentation/filesystems/afs.rst> for more information.
+
+	  If unsure, say N.
+
+config AFS_DEBUG
+	bool "AFS dynamic debugging"
+	depends on AFS_FS
+	help
+	  Say Y here to make runtime controllable debugging messages appear.
+
+	  See <file:Documentation/filesystems/afs.rst> for more information.
+
+	  If unsure, say N.
+
+config AFS_FSCACHE
+	bool "Provide AFS client caching support"
+	depends on AFS_FS=m && FSCACHE || AFS_FS=y && FSCACHE=y
+	help
+	  Say Y here if you want AFS data to be cached locally on disk through
+	  the generic filesystem cache manager
+
+config AFS_DEBUG_CURSOR
+	bool "AFS server cursor debugging"
+	depends on AFS_FS
+	help
+	  Say Y here to cause the contents of a server cursor to be dumped to
+	  the dmesg log if the server rotation algorithm fails to successfully
+	  contact a server.
+
+	  See <file:Documentation/filesystems/afs.rst> for more information.
+
+	  If unsure, say N.