From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall 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 Signed-off-by: Stafford Horne --- Documentation/ABI/testing/sysfs-kernel-mm-ksm | 61 +++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-ksm (limited to 'Documentation/ABI/testing/sysfs-kernel-mm-ksm') diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm new file mode 100644 index 000000000..6041a025b --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm @@ -0,0 +1,61 @@ +What: /sys/kernel/mm/ksm +Date: September 2009 +KernelVersion: 2.6.32 +Contact: Linux memory management mailing list +Description: Interface for Kernel Samepage Merging (KSM) + +What: /sys/kernel/mm/ksm/full_scans +What: /sys/kernel/mm/ksm/pages_shared +What: /sys/kernel/mm/ksm/pages_sharing +What: /sys/kernel/mm/ksm/pages_to_scan +What: /sys/kernel/mm/ksm/pages_unshared +What: /sys/kernel/mm/ksm/pages_volatile +What: /sys/kernel/mm/ksm/run +What: /sys/kernel/mm/ksm/sleep_millisecs +Date: September 2009 +Contact: Linux memory management mailing list +Description: Kernel Samepage Merging daemon sysfs interface + + full_scans: how many times all mergeable areas have been + scanned. + + pages_shared: how many shared pages are being used. + + pages_sharing: how many more sites are sharing them i.e. how + much saved. + + pages_to_scan: how many present pages to scan before ksmd goes + to sleep. + + pages_unshared: how many pages unique but repeatedly checked + for merging. + + pages_volatile: how many pages changing too fast to be placed + in a tree. + + run: write 0 to disable ksm, read 0 while ksm is disabled. + + - write 1 to run ksm, read 1 while ksm is running. + - write 2 to disable ksm and unmerge all its pages. + + sleep_millisecs: how many milliseconds ksm should sleep between + scans. + + See Documentation/mm/ksm.rst for more information. + +What: /sys/kernel/mm/ksm/merge_across_nodes +Date: January 2013 +KernelVersion: 3.9 +Contact: Linux memory management mailing list +Description: Control merging pages across different NUMA nodes. + + When it is set to 0 only pages from the same node are merged, + otherwise pages from all nodes can be merged together (default). + +What: /sys/kernel/mm/ksm/general_profit +Date: April 2023 +KernelVersion: 6.4 +Contact: Linux memory management mailing list +Description: Measure how effective KSM is. + general_profit: how effective is KSM. The formula for the + calculation is in Documentation/admin-guide/mm/ksm.rst. -- cgit v1.3.1