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 --- fs/proc/kmsg.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 fs/proc/kmsg.c (limited to 'fs/proc/kmsg.c') diff --git a/fs/proc/kmsg.c b/fs/proc/kmsg.c new file mode 100644 index 000000000..2fc92a13f --- /dev/null +++ b/fs/proc/kmsg.c @@ -0,0 +1,63 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/proc/kmsg.c + * + * Copyright (C) 1992 by Linus Torvalds + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +static int kmsg_open(struct inode * inode, struct file * file) +{ + return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC); +} + +static int kmsg_release(struct inode * inode, struct file * file) +{ + (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC); + return 0; +} + +static ssize_t kmsg_read(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + if ((file->f_flags & O_NONBLOCK) && + !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) + return -EAGAIN; + return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC); +} + +static __poll_t kmsg_poll(struct file *file, poll_table *wait) +{ + poll_wait(file, &log_wait, wait); + if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC)) + return EPOLLIN | EPOLLRDNORM; + return 0; +} + + +static const struct proc_ops kmsg_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, + .proc_read = kmsg_read, + .proc_poll = kmsg_poll, + .proc_open = kmsg_open, + .proc_release = kmsg_release, + .proc_lseek = generic_file_llseek, +}; + +static int __init proc_kmsg_init(void) +{ + proc_create("kmsg", S_IRUSR, NULL, &kmsg_proc_ops); + return 0; +} +fs_initcall(proc_kmsg_init); -- cgit v1.3.1