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, 30 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-spi-eeprom b/Documentation/ABI/testing/sysfs-class-spi-eeprom
new file mode 100644
index 000000000..f4bc7d945
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-spi-eeprom
@@ -0,0 +1,30 @@
+What:		/sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fram
+Date:		June 2021
+KernelVersion:	5.14
+Contact:	Jiri Prchal <jiri.prchal@aksignal.cz>
+Description:
+	Contains the FRAM binary data. Same as EEPROM, just another file
+	name to indicate that it employs ferroelectric process.
+	It performs write operations at bus speed - no write delays.
+
+What:		/sys/class/spi_master/spi<bus>/spi<bus>.<dev>/sernum
+Date:		May 2021
+KernelVersion:	5.14
+Contact:	Jiri Prchal <jiri.prchal@aksignal.cz>
+Description:
+	Contains the serial number of the Cypress FRAM (FM25VN) if it is
+	present.  It will be displayed as a 8 byte hex string, as read
+	from the device.
+
+	This is a read-only attribute.
+
+What:		/sys/class/spi_master/spi<bus>/spi<bus>.<dev>/jedec_id
+Date:		January 2026
+KernelVersion:	6.19
+Contact:	Patrick Wicki <patrick.wicki@siemens.com>
+Description:
+	Contains the raw JEDEC ID bytes returned by the RDID (0x9f) command. The
+	bytes are exposed as a hex string in big-endian order as read from the
+	device.
+
+	This is a read-only attribute.