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/arm/lib/memset.S | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 148 insertions(+) create mode 100644 arch/arm/lib/memset.S (limited to 'arch/arm/lib/memset.S') diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S new file mode 100644 index 000000000..de75ae4d5 --- /dev/null +++ b/arch/arm/lib/memset.S @@ -0,0 +1,148 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/memset.S + * + * Copyright (C) 1995-2000 Russell King + * + * ASM optimised string functions + */ +#include +#include +#include + + .text + .align 5 + +ENTRY(__memset) +ENTRY(mmioset) +WEAK(memset) +UNWIND( .fnstart ) + and r1, r1, #255 @ cast to unsigned char + ands r3, r0, #3 @ 1 unaligned? + mov ip, r0 @ preserve r0 as return value + bne 6f @ 1 +/* + * we know that the pointer in ip is aligned to a word boundary. + */ +1: orr r1, r1, r1, lsl #8 + orr r1, r1, r1, lsl #16 + mov r3, r1 +7: cmp r2, #16 + blt 4f +UNWIND( .fnend ) + +#if ! CALGN(1)+0 + +/* + * We need 2 extra registers for this loop - use r8 and the LR + */ +UNWIND( .fnstart ) +UNWIND( .save {r8, lr} ) + stmfd sp!, {r8, lr} + mov r8, r1 + mov lr, r3 + +2: subs r2, r2, #64 + stmiage ip!, {r1, r3, r8, lr} @ 64 bytes at a time. + stmiage ip!, {r1, r3, r8, lr} + stmiage ip!, {r1, r3, r8, lr} + stmiage ip!, {r1, r3, r8, lr} + bgt 2b + ldmfdeq sp!, {r8, pc} @ Now <64 bytes to go. +/* + * No need to correct the count; we're only testing bits from now on + */ + tst r2, #32 + stmiane ip!, {r1, r3, r8, lr} + stmiane ip!, {r1, r3, r8, lr} + tst r2, #16 + stmiane ip!, {r1, r3, r8, lr} + ldmfd sp!, {r8, lr} +UNWIND( .fnend ) + +#else + +/* + * This version aligns the destination pointer in order to write + * whole cache lines at once. + */ + +UNWIND( .fnstart ) +UNWIND( .save {r4-r8, lr} ) + stmfd sp!, {r4-r8, lr} + mov r4, r1 + mov r5, r3 + mov r6, r1 + mov r7, r3 + mov r8, r1 + mov lr, r3 + + cmp r2, #96 + tstgt ip, #31 + ble 3f + + and r8, ip, #31 + rsb r8, r8, #32 + sub r2, r2, r8 + movs r8, r8, lsl #(32 - 4) + stmiacs ip!, {r4, r5, r6, r7} + stmiami ip!, {r4, r5} + tst r8, #(1 << 30) + mov r8, r1 + strne r1, [ip], #4 + +3: subs r2, r2, #64 + stmiage ip!, {r1, r3-r8, lr} + stmiage ip!, {r1, r3-r8, lr} + bgt 3b + ldmfdeq sp!, {r4-r8, pc} + + tst r2, #32 + stmiane ip!, {r1, r3-r8, lr} + tst r2, #16 + stmiane ip!, {r4-r7} + ldmfd sp!, {r4-r8, lr} +UNWIND( .fnend ) + +#endif + +UNWIND( .fnstart ) +4: tst r2, #8 + stmiane ip!, {r1, r3} + tst r2, #4 + strne r1, [ip], #4 +/* + * When we get here, we've got less than 4 bytes to set. We + * may have an unaligned pointer as well. + */ +5: tst r2, #2 + strbne r1, [ip], #1 + strbne r1, [ip], #1 + tst r2, #1 + strbne r1, [ip], #1 + ret lr + +6: subs r2, r2, #4 @ 1 do we have enough + blt 5b @ 1 bytes to align with? + cmp r3, #2 @ 1 + strblt r1, [ip], #1 @ 1 + strble r1, [ip], #1 @ 1 + strb r1, [ip], #1 @ 1 + add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3)) + b 1b +UNWIND( .fnend ) +ENDPROC(memset) +ENDPROC(mmioset) +ENDPROC(__memset) + +ENTRY(__memset32) +UNWIND( .fnstart ) + mov r3, r1 @ copy r1 to r3 and fall into memset64 +UNWIND( .fnend ) +ENDPROC(__memset32) +ENTRY(__memset64) +UNWIND( .fnstart ) + mov ip, r0 @ preserve r0 as return value + b 7b @ jump into the middle of memset +UNWIND( .fnend ) +ENDPROC(__memset64) -- cgit v1.3.1