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/s390/char/ctrlchar.c | 80 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 drivers/s390/char/ctrlchar.c (limited to 'drivers/s390/char/ctrlchar.c') diff --git a/drivers/s390/char/ctrlchar.c b/drivers/s390/char/ctrlchar.c new file mode 100644 index 000000000..6f2b64040 --- /dev/null +++ b/drivers/s390/char/ctrlchar.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Unified handling of special chars. + * + * Copyright IBM Corp. 2001 + * Author(s): Fritz Elfert + * + */ + +#include +#include +#include +#include + +#include "ctrlchar.h" + +#ifdef CONFIG_MAGIC_SYSRQ +static struct sysrq_work ctrlchar_sysrq; + +static void +ctrlchar_handle_sysrq(struct work_struct *work) +{ + struct sysrq_work *sysrq = container_of(work, struct sysrq_work, work); + + handle_sysrq(sysrq->key); +} + +void schedule_sysrq_work(struct sysrq_work *sw) +{ + INIT_WORK(&sw->work, ctrlchar_handle_sysrq); + schedule_work(&sw->work); +} +#endif + + +/** + * ctrlchar_handle - check for special chars at start of input + * + * @buf: console input buffer + * @len: length of valid data in buffer + * @tty: the tty struct for this console + * + * Return: CTRLCHAR_NONE, if nothing matched, + * CTRLCHAR_SYSRQ, if sysrq was encountered + * otherwise char to be inserted logically or'ed + * with CTRLCHAR_CTRL + */ +unsigned int +ctrlchar_handle(const unsigned char *buf, int len, struct tty_struct *tty) +{ + if ((len < 2) || (len > 3)) + return CTRLCHAR_NONE; + + /* hat is 0xb1 in codepage 037 (US etc.) and thus */ + /* converted to 0x5e in ascii ('^') */ + if ((buf[0] != '^') && (buf[0] != '\252')) + return CTRLCHAR_NONE; + +#ifdef CONFIG_MAGIC_SYSRQ + /* racy */ + if (len == 3 && buf[1] == '-') { + ctrlchar_sysrq.key = buf[2]; + schedule_sysrq_work(&ctrlchar_sysrq); + return CTRLCHAR_SYSRQ; + } +#endif + + if (len != 2) + return CTRLCHAR_NONE; + + switch (tolower(buf[1])) { + case 'c': + return INTR_CHAR(tty) | CTRLCHAR_CTRL; + case 'd': + return EOF_CHAR(tty) | CTRLCHAR_CTRL; + case 'z': + return SUSP_CHAR(tty) | CTRLCHAR_CTRL; + } + return CTRLCHAR_NONE; +} -- cgit v1.3.1