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, 59 insertions, 0 deletions

diff --git a/Documentation/block/error-injection.rst b/Documentation/block/error-injection.rst
new file mode 100644
index 000000000..81f31af82
--- /dev/null
+++ b/Documentation/block/error-injection.rst
@@ -0,0 +1,59 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================
+Configurable Error Injection
+============================
+
+Overview
+--------
+
+Configurable error injection allows injecting specific block layer status codes
+for sector ranges of a block device.  Errors can be injected unconditionally, or
+with a given probability.
+
+To use configurable error injection, CONFIG_BLK_ERROR_INJECTION must be enabled.
+
+The only interface is the error_injection debugfs file, which is created for
+each registered gendisk.  Writes to this file are used to create or delete rules
+and reads return a list of the current error injection sites.
+
+Options
+-------
+
+The following options specify the operations:
+
+===================	=======================================================
+add			add a new rule
+removeall		remove all existing rules
+===================	=======================================================
+
+The following options specify the details of the rule for the add operation:
+
+===================	=======================================================
+op=<string>		block layer operation this rule applies to.  This uses
+			the XYZ for each REQ_OP_XYZ operation, e.g. READ, WRITE
+			or DISCARD. Mandatory.
+status=<string>		Status to return.  This uses XYZ for each BLK_STS_XYZ
+			code, e.g. IOERR or MEDIUM. Mandatory.
+start=<number>		First block layer sector the rule applies to.
+			Optional, defaults to 0.
+nr_sectors=<number>	Number of sectors this rule applies.
+			Optional, defaults to the remainder of the device.
+chance=<number>		Only return a failure with a likelihood of 1/chance.
+			Optional, defaults to 1 (always).
+===================	=======================================================
+
+Example
+-------
+
+Return BLK_STS_IOERR for one in 10 reads of sector 0 of /dev/nvme0n1:
+
+	$ echo 'add,op=READ,start=0,status=IOERR,chance=10' > /sys/kernel/debug/block/nvme0n1/error_injection
+
+Return BLK_STS_MEDIUM for every write to /dev/nvme0n1:
+
+	$ echo 'add,op=WRITE,start=0,status=MEDIUM' > /sys/kernel/debug/block/nvme0n1/error_injection
+
+Remove all rules for /dev/nvme0n1:
+
+	$ echo 'removeall' > /sys/kernel/debug/block/nvme0n1/error_injection