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/ashldi3.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 arch/microblaze/lib/ashldi3.c (limited to 'arch/microblaze/lib/ashldi3.c') diff --git a/arch/microblaze/lib/ashldi3.c b/arch/microblaze/lib/ashldi3.c new file mode 100644 index 000000000..4d0f9481b --- /dev/null +++ b/arch/microblaze/lib/ashldi3.c @@ -0,0 +1,29 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +#include "libgcc.h" + +long long __ashldi3(long long u, word_type b) +{ + DWunion uu, w; + word_type bm; + + if (b == 0) + return u; + + uu.ll = u; + bm = 32 - b; + + if (bm <= 0) { + w.s.low = 0; + w.s.high = (unsigned int) uu.s.low << -bm; + } else { + const unsigned int carries = (unsigned int) uu.s.low >> bm; + + w.s.low = (unsigned int) uu.s.low << b; + w.s.high = ((unsigned int) uu.s.high << b) | carries; + } + + return w.ll; +} +EXPORT_SYMBOL(__ashldi3); -- cgit v1.3.1