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 --- tools/perf/util/cap.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 tools/perf/util/cap.c (limited to 'tools/perf/util/cap.c') diff --git a/tools/perf/util/cap.c b/tools/perf/util/cap.c new file mode 100644 index 000000000..ac6d1d9a5 --- /dev/null +++ b/tools/perf/util/cap.c @@ -0,0 +1,48 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Capability utilities + */ + +#include "cap.h" +#include "debug.h" +#include +#include +#include +#include + +#define MAX_LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3 + +bool perf_cap__capable(int cap, bool *used_root) +{ + struct __user_cap_header_struct header = { + .version = _LINUX_CAPABILITY_VERSION_3, + .pid = 0, + }; + struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S] = {}; + __u32 cap_val; + + *used_root = false; + while (syscall(SYS_capget, &header, &data[0]) == -1) { + /* Retry, first attempt has set the header.version correctly. */ + if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 && + header.version == _LINUX_CAPABILITY_VERSION_1) + continue; + + pr_debug2("capget syscall failed (%m) fall back on root check\n"); + *used_root = true; + return geteuid() == 0; + } + + /* Extract the relevant capability bit. */ + if (cap >= 32) { + if (header.version == _LINUX_CAPABILITY_VERSION_3) { + cap_val = data[1].effective; + } else { + /* Capability beyond 32 is requested but only 32 are supported. */ + return false; + } + } else { + cap_val = data[0].effective; + } + return (cap_val & (1 << (cap & 0x1f))) != 0; +} -- cgit v1.3.1