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/microblaze/lib/cmpdi2.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 arch/microblaze/lib/cmpdi2.c (limited to 'arch/microblaze/lib/cmpdi2.c') diff --git a/arch/microblaze/lib/cmpdi2.c b/arch/microblaze/lib/cmpdi2.c new file mode 100644 index 000000000..b3f896385 --- /dev/null +++ b/arch/microblaze/lib/cmpdi2.c @@ -0,0 +1,27 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +#include "libgcc.h" + +word_type __cmpdi2(long long a, long long b) +{ + const DWunion au = { + .ll = a + }; + const DWunion bu = { + .ll = b + }; + + if (au.s.high < bu.s.high) + return 0; + else if (au.s.high > bu.s.high) + return 2; + + if ((unsigned int) au.s.low < (unsigned int) bu.s.low) + return 0; + else if ((unsigned int) au.s.low > (unsigned int) bu.s.low) + return 2; + + return 1; +} +EXPORT_SYMBOL(__cmpdi2); -- cgit v1.3.1