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/xtensa/lib/ashrdi3.S | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 arch/xtensa/lib/ashrdi3.S (limited to 'arch/xtensa/lib/ashrdi3.S') diff --git a/arch/xtensa/lib/ashrdi3.S b/arch/xtensa/lib/ashrdi3.S new file mode 100644 index 000000000..07bc6e758 --- /dev/null +++ b/arch/xtensa/lib/ashrdi3.S @@ -0,0 +1,29 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */ +#include +#include +#include + +#ifdef __XTENSA_EB__ +#define uh a2 +#define ul a3 +#else +#define uh a3 +#define ul a2 +#endif /* __XTENSA_EB__ */ + +ENTRY(__ashrdi3) + + abi_entry_default + ssr a4 + bgei a4, 32, .Lhigh_only + src ul, uh, ul + sra uh, uh + abi_ret_default + +.Lhigh_only: + sra ul, uh + srai uh, uh, 31 + abi_ret_default + +ENDPROC(__ashrdi3) +EXPORT_SYMBOL(__ashrdi3) -- cgit v1.3.1