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 --- include/asm-generic/bitops/atomic.h | 70 +++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 include/asm-generic/bitops/atomic.h (limited to 'include/asm-generic/bitops/atomic.h') diff --git a/include/asm-generic/bitops/atomic.h b/include/asm-generic/bitops/atomic.h new file mode 100644 index 000000000..e076e079f --- /dev/null +++ b/include/asm-generic/bitops/atomic.h @@ -0,0 +1,70 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_BITOPS_ATOMIC_H_ +#define _ASM_GENERIC_BITOPS_ATOMIC_H_ + +#include +#include +#include + +/* + * Implementation of atomic bitops using atomic-fetch ops. + * See Documentation/atomic_bitops.txt for details. + */ + +static __always_inline void +arch_set_bit(unsigned int nr, volatile unsigned long *p) +{ + p += BIT_WORD(nr); + raw_atomic_long_or(BIT_MASK(nr), (atomic_long_t *)p); +} + +static __always_inline void +arch_clear_bit(unsigned int nr, volatile unsigned long *p) +{ + p += BIT_WORD(nr); + raw_atomic_long_andnot(BIT_MASK(nr), (atomic_long_t *)p); +} + +static __always_inline void +arch_change_bit(unsigned int nr, volatile unsigned long *p) +{ + p += BIT_WORD(nr); + raw_atomic_long_xor(BIT_MASK(nr), (atomic_long_t *)p); +} + +static __always_inline int +arch_test_and_set_bit(unsigned int nr, volatile unsigned long *p) +{ + long old; + unsigned long mask = BIT_MASK(nr); + + p += BIT_WORD(nr); + old = raw_atomic_long_fetch_or(mask, (atomic_long_t *)p); + return !!(old & mask); +} + +static __always_inline int +arch_test_and_clear_bit(unsigned int nr, volatile unsigned long *p) +{ + long old; + unsigned long mask = BIT_MASK(nr); + + p += BIT_WORD(nr); + old = raw_atomic_long_fetch_andnot(mask, (atomic_long_t *)p); + return !!(old & mask); +} + +static __always_inline int +arch_test_and_change_bit(unsigned int nr, volatile unsigned long *p) +{ + long old; + unsigned long mask = BIT_MASK(nr); + + p += BIT_WORD(nr); + old = raw_atomic_long_fetch_xor(mask, (atomic_long_t *)p); + return !!(old & mask); +} + +#include + +#endif /* _ASM_GENERIC_BITOPS_ATOMIC_H */ -- cgit v1.3.1