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/admin-guide/sysctl/debug.rst | 52 ++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/admin-guide/sysctl/debug.rst (limited to 'Documentation/admin-guide/sysctl/debug.rst') diff --git a/Documentation/admin-guide/sysctl/debug.rst b/Documentation/admin-guide/sysctl/debug.rst new file mode 100644 index 000000000..506bd5e48 --- /dev/null +++ b/Documentation/admin-guide/sysctl/debug.rst @@ -0,0 +1,52 @@ +================ +/proc/sys/debug/ +================ + +These files show up in ``/proc/sys/debug/``, depending on the +kernel configuration: + +.. contents:: :local: + +exception-trace +=============== + +This flag controls whether the kernel prints information about unhandled +signals (like segmentation faults) to the kernel log (``dmesg``). + +- ``0``: Unhandled signals are not traced. +- ``1``: Information about unhandled signals is printed. + +The default value is ``1`` on most architectures (like x86, MIPS, RISC-V), +but it is ``0`` on **arm64**. + +The actual information printed and the context provided varies +significantly depending on the CPU architecture. For example: + +- On **x86**, it typically prints the instruction pointer (IP), error + code, and address that caused a page fault. +- On **PowerPC**, it may print the next instruction pointer (NIP), + link register (LR), and other relevant registers. + +When enabled, this feature is often rate-limited to prevent the kernel +log from being flooded during a crash loop. + +kprobes-optimization +==================== + +This flag enables or disables the optimization of Kprobes on certain +architectures (like x86). + +- ``0``: Kprobes optimization is turned off. +- ``1``: Kprobes optimization is turned on (default). + +For more details on Kprobes and its optimization, please refer to +Documentation/trace/kprobes.rst. + +Copyright (c) 2026, Shubham Chakraborty + +For general info and legal blurb, please look in +Documentation/admin-guide/sysctl/index.rst. + +.. See scripts/check-sysctl-docs to keep this up to date: +.. scripts/check-sysctl-docs -vtable="debug" \ +.. $(git grep -l register_sysctl_) -- cgit v1.3.1