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 --- security/min_addr.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 security/min_addr.c (limited to 'security/min_addr.c') diff --git a/security/min_addr.c b/security/min_addr.c new file mode 100644 index 000000000..56e4f9d25 --- /dev/null +++ b/security/min_addr.c @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +/* amount of vm to protect from userspace access by both DAC and the LSM*/ +unsigned long mmap_min_addr; +/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */ +unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR; +/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */ + +/* + * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR) + */ +static void update_mmap_min_addr(void) +{ +#ifdef CONFIG_LSM_MMAP_MIN_ADDR + mmap_min_addr = umax(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR); +#else + mmap_min_addr = dac_mmap_min_addr; +#endif +} + +/* + * sysctl handler which just sets dac_mmap_min_addr = the new value and then + * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly + */ +int mmap_min_addr_handler(const struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int ret; + + if (write && !capable(CAP_SYS_RAWIO)) + return -EPERM; + + ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); + + update_mmap_min_addr(); + + return ret; +} + +static const struct ctl_table min_addr_sysctl_table[] = { + { + .procname = "mmap_min_addr", + .data = &dac_mmap_min_addr, + .maxlen = sizeof(unsigned long), + .mode = 0644, + .proc_handler = mmap_min_addr_handler, + }, +}; + +static int __init mmap_min_addr_init(void) +{ + register_sysctl_init("vm", min_addr_sysctl_table); + update_mmap_min_addr(); + + return 0; +} +pure_initcall(mmap_min_addr_init); -- cgit v1.3.1