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/bitsperlong.h | 47 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) create mode 100644 include/asm-generic/bitsperlong.h (limited to 'include/asm-generic/bitsperlong.h') diff --git a/include/asm-generic/bitsperlong.h b/include/asm-generic/bitsperlong.h new file mode 100644 index 000000000..90e8aeebf --- /dev/null +++ b/include/asm-generic/bitsperlong.h @@ -0,0 +1,47 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_GENERIC_BITS_PER_LONG +#define __ASM_GENERIC_BITS_PER_LONG + +#include + + +#ifdef CONFIG_64BIT +#define BITS_PER_LONG 64 +#else +#define BITS_PER_LONG 32 +#endif /* CONFIG_64BIT */ + +/* + * FIXME: The check currently breaks x86-64 build, so it's + * temporarily disabled. Please fix x86-64 and reenable + */ +#if 0 && BITS_PER_LONG != __BITS_PER_LONG +#error Inconsistent word size. Check asm/bitsperlong.h +#endif + +#if __CHAR_BIT__ * __SIZEOF_LONG__ != __BITS_PER_LONG +#error Inconsistent word size. Check asm/bitsperlong.h +#endif + +#ifndef __ASSEMBLER__ +_Static_assert(sizeof(long) * 8 == __BITS_PER_LONG, + "Inconsistent word size. Check asm/bitsperlong.h"); +#endif + +#ifndef BITS_PER_LONG_LONG +#define BITS_PER_LONG_LONG 64 +#endif + +/* + * small_const_nbits(n) is true precisely when it is known at compile-time + * that BITMAP_SIZE(n) is 1, i.e. 1 <= n <= BITS_PER_LONG. This allows + * various bit/bitmap APIs to provide a fast inline implementation. Bitmaps + * of size 0 are very rare, and a compile-time-known-size 0 is most likely + * a sign of error. They will be handled correctly by the bit/bitmap APIs, + * but using the out-of-line functions, so that the inline implementations + * can unconditionally dereference the pointer(s). + */ +#define small_const_nbits(nbits) \ + (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) + +#endif /* __ASM_GENERIC_BITS_PER_LONG */ -- cgit v1.3.1