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 --- arch/powerpc/lib/locks.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 arch/powerpc/lib/locks.c (limited to 'arch/powerpc/lib/locks.c') diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c new file mode 100644 index 000000000..04165b7a1 --- /dev/null +++ b/arch/powerpc/lib/locks.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Spin and read/write lock operations. + * + * Copyright (C) 2001-2004 Paul Mackerras , IBM + * Copyright (C) 2001 Anton Blanchard , IBM + * Copyright (C) 2002 Dave Engebretsen , IBM + * Rework to support virtual processors + */ + +#include +#include +#include +#include + +/* waiting for a spinlock... */ +#if defined(CONFIG_PPC_SPLPAR) +#include +#include + +void splpar_spin_yield(arch_spinlock_t *lock) +{ + unsigned int lock_value, holder_cpu, yield_count; + + lock_value = lock->slock; + if (lock_value == 0) + return; + holder_cpu = lock_value & 0xffff; + BUG_ON(holder_cpu >= NR_CPUS); + + yield_count = yield_count_of(holder_cpu); + if ((yield_count & 1) == 0) + return; /* virtual cpu is currently running */ + rmb(); + if (lock->slock != lock_value) + return; /* something has changed */ + yield_to_preempted(holder_cpu, yield_count); +} +EXPORT_SYMBOL_GPL(splpar_spin_yield); + +/* + * Waiting for a read lock or a write lock on a rwlock... + * This turns out to be the same for read and write locks, since + * we only know the holder if it is write-locked. + */ +void splpar_rw_yield(arch_rwlock_t *rw) +{ + int lock_value; + unsigned int holder_cpu, yield_count; + + lock_value = rw->lock; + if (lock_value >= 0) + return; /* no write lock at present */ + holder_cpu = lock_value & 0xffff; + BUG_ON(holder_cpu >= NR_CPUS); + + yield_count = yield_count_of(holder_cpu); + if ((yield_count & 1) == 0) + return; /* virtual cpu is currently running */ + rmb(); + if (rw->lock != lock_value) + return; /* something has changed */ + yield_to_preempted(holder_cpu, yield_count); +} +#endif -- cgit v1.3.1