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, 41 insertions, 0 deletions

diff --git a/Documentation/process/conclave.rst b/Documentation/process/conclave.rst
new file mode 100644
index 000000000..6a1234f54
--- /dev/null
+++ b/Documentation/process/conclave.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+Linux kernel project continuity
+===============================
+
+The Linux kernel development project is widely distributed, with over
+100 maintainers each working to keep changes moving through their own
+repositories. The final step, though, is a centralized one where changes
+are pulled into the mainline repository. That is normally done by Linus
+Torvalds but, as was demonstrated by the 4.19 release in 2018, there are
+others who can do that work when the need arises.
+
+Should the maintainers of that repository become unwilling or unable to
+do that work going forward (including facilitating a transition), the
+project will need to find one or more replacements without delay. The
+process by which that will be done is listed below. $ORGANIZER is the
+last Maintainer Summit organizer or the current Linux Foundation (LF)
+Technical Advisory Board (TAB) Chair as a backup.
+
+- Within 72 hours, $ORGANIZER will open a discussion with the invitees
+  of the most recently concluded Maintainers Summit. A meeting of those
+  invitees and the TAB, either online or in-person, will be set as soon
+  as possible in a way that maximizes the number of people who can
+  participate.
+
+- If there has been no Maintainers Summit in the last 15 months, the set of
+  invitees for this meeting will be determined by the TAB.
+
+- The invitees to this meeting may bring in other maintainers as needed.
+
+- This meeting, chaired by $ORGANIZER, will consider options for the
+  ongoing management of the top-level kernel repository consistent with
+  the expectation that it maximizes the long term health of the project
+  and its community.
+
+- Within two weeks, a representative of this group will communicate to the
+  broader community, using the ksummit@lists.linux.dev mailing list, what
+  the next steps will be.
+
+The Linux Foundation, as guided by the TAB, will take the steps
+necessary to support and implement this plan.