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 --- drivers/clk/tegra/clk-utils.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 drivers/clk/tegra/clk-utils.c (limited to 'drivers/clk/tegra/clk-utils.c') diff --git a/drivers/clk/tegra/clk-utils.c b/drivers/clk/tegra/clk-utils.c new file mode 100644 index 000000000..1a5daae4e --- /dev/null +++ b/drivers/clk/tegra/clk-utils.c @@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved. + */ + +#include + +#include "clk.h" + +#define div_mask(w) ((1 << (w)) - 1) + +int div_frac_get(unsigned long rate, unsigned parent_rate, u8 width, + u8 frac_width, u8 flags) +{ + u64 divider_ux1 = parent_rate; + int mul; + + if (!rate) + return 0; + + mul = 1 << frac_width; + + if (!(flags & TEGRA_DIVIDER_INT)) + divider_ux1 *= mul; + + if (flags & TEGRA_DIVIDER_ROUND_UP) + divider_ux1 += rate - 1; + + do_div(divider_ux1, rate); + + if (flags & TEGRA_DIVIDER_INT) + divider_ux1 *= mul; + + if (divider_ux1 < mul) + return 0; + + divider_ux1 -= mul; + + if (divider_ux1 > div_mask(width)) + return div_mask(width); + + return divider_ux1; +} -- cgit v1.3.1