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/firmware/efi/ovmf-debug-log.c | 111 ++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 drivers/firmware/efi/ovmf-debug-log.c (limited to 'drivers/firmware/efi/ovmf-debug-log.c') diff --git a/drivers/firmware/efi/ovmf-debug-log.c b/drivers/firmware/efi/ovmf-debug-log.c new file mode 100644 index 000000000..5b2471ffa --- /dev/null +++ b/drivers/firmware/efi/ovmf-debug-log.c @@ -0,0 +1,111 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include + +#define OVMF_DEBUG_LOG_MAGIC1 0x3167646d666d766f // "ovmfmdg1" +#define OVMF_DEBUG_LOG_MAGIC2 0x3267646d666d766f // "ovmfmdg2" + +struct ovmf_debug_log_header { + u64 magic1; + u64 magic2; + u64 hdr_size; + u64 log_size; + u64 lock; // edk2 spinlock + u64 head_off; + u64 tail_off; + u64 truncated; + u8 fw_version[128]; +}; + +static struct ovmf_debug_log_header *hdr; +static u8 *logbuf; +static u64 logbufsize; + +static ssize_t ovmf_log_read(struct file *filp, struct kobject *kobj, + const struct bin_attribute *attr, char *buf, + loff_t offset, size_t count) +{ + u64 start, end; + + start = hdr->head_off + offset; + if (hdr->head_off > hdr->tail_off && start >= hdr->log_size) + start -= hdr->log_size; + + end = start + count; + if (start > hdr->tail_off) { + if (end > hdr->log_size) + end = hdr->log_size; + } else { + if (end > hdr->tail_off) + end = hdr->tail_off; + } + + if (start > logbufsize || end > logbufsize) + return 0; + if (start >= end) + return 0; + + memcpy(buf, logbuf + start, end - start); + return end - start; +} + +static struct bin_attribute ovmf_log_bin_attr = { + .attr = { + .name = "ovmf_debug_log", + .mode = 0444, + }, + .read = ovmf_log_read, +}; + +int __init ovmf_log_probe(unsigned long ovmf_debug_log_table) +{ + int ret = -EINVAL; + u64 size; + + /* map + verify header */ + hdr = memremap(ovmf_debug_log_table, sizeof(*hdr), MEMREMAP_WB); + if (!hdr) { + pr_err("OVMF debug log: header map failed\n"); + return -EINVAL; + } + + if (hdr->magic1 != OVMF_DEBUG_LOG_MAGIC1 || + hdr->magic2 != OVMF_DEBUG_LOG_MAGIC2) { + printk(KERN_ERR "OVMF debug log: magic mismatch\n"); + goto err_unmap; + } + + size = hdr->hdr_size + hdr->log_size; + pr_info("OVMF debug log: firmware version: \"%s\"\n", hdr->fw_version); + pr_info("OVMF debug log: buffer size: %lluk\n", size / 1024); + + /* map complete log buffer */ + memunmap(hdr); + hdr = memremap(ovmf_debug_log_table, size, MEMREMAP_WB); + if (!hdr) { + pr_err("OVMF debug log: buffer map failed\n"); + return -EINVAL; + } + logbuf = (void *)hdr + hdr->hdr_size; + logbufsize = hdr->log_size; + + ovmf_log_bin_attr.size = size; + ret = sysfs_create_bin_file(efi_kobj, &ovmf_log_bin_attr); + if (ret != 0) { + pr_err("OVMF debug log: sysfs register failed\n"); + goto err_unmap; + } + + return 0; + +err_unmap: + memunmap(hdr); + return ret; +} -- cgit v1.3.1