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/removed/sysfs-mce | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 Documentation/ABI/removed/sysfs-mce (limited to 'Documentation/ABI/removed/sysfs-mce') diff --git a/Documentation/ABI/removed/sysfs-mce b/Documentation/ABI/removed/sysfs-mce new file mode 100644 index 000000000..ef5dd2a80 --- /dev/null +++ b/Documentation/ABI/removed/sysfs-mce @@ -0,0 +1,37 @@ +What: /sys/devices/system/machinecheck/machinecheckX/tolerant +Contact: Borislav Petkov +Date: Dec, 2021 +Description: + Unused and obsolete after the advent of recoverable machine + checks (see last sentence below) and those are present since + 2010 (Nehalem). + + Original description: + + The entries appear for each CPU, but they are truly shared + between all CPUs. + + Tolerance level. When a machine check exception occurs for a + non corrected machine check the kernel can take different + actions. + + Since machine check exceptions can happen any time it is + sometimes risky for the kernel to kill a process because it + defies normal kernel locking rules. The tolerance level + configures how hard the kernel tries to recover even at some + risk of deadlock. Higher tolerant values trade potentially + better uptime with the risk of a crash or even corruption + (for tolerant >= 3). + + == =========================================================== + 0 always panic on uncorrected errors, log corrected errors + 1 panic or SIGBUS on uncorrected errors, log corrected errors + 2 SIGBUS or log uncorrected errors, log corrected errors + 3 never panic or SIGBUS, log all errors (for testing only) + == =========================================================== + + Default: 1 + + Note this only makes a difference if the CPU allows recovery + from a machine check exception. Current x86 CPUs generally + do not. -- cgit v1.3.1