diff options
Diffstat (limited to 'arch/um/os-Linux')
| -rw-r--r-- | arch/um/os-Linux/mem.c | 2 | ||||
| -rw-r--r-- | arch/um/os-Linux/skas/process.c | 177 |
2 files changed, 122 insertions, 57 deletions
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c index cf44d386f23c..857e3deab293 100644 --- a/arch/um/os-Linux/mem.c +++ b/arch/um/os-Linux/mem.c @@ -42,7 +42,7 @@ void kasan_map_memory(void *start, size_t len) } /* Set by make_tempfile() during early boot. */ -static char *tempdir = NULL; +char *tempdir = NULL; /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */ static int __init check_tmpfs(const char *dir) diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index be666e02c44f..2286486bb0f3 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -10,8 +10,11 @@ #include <sched.h> #include <errno.h> #include <string.h> +#include <fcntl.h> +#include <mem_user.h> #include <sys/mman.h> #include <sys/wait.h> +#include <sys/stat.h> #include <asm/unistd.h> #include <as-layout.h> #include <init.h> @@ -176,69 +179,131 @@ static void handle_trap(int pid, struct uml_pt_regs *regs) extern char __syscall_stub_start[]; -/** - * userspace_tramp() - userspace trampoline - * @stack: pointer to the new userspace stack page - * - * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed. - * This function will run on a temporary stack page. - * It ptrace()'es itself, then - * Two pages are mapped into the userspace address space: - * - STUB_CODE (with EXEC), which contains the skas stub code - * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel. - * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process. - * And last the process stops itself to give control to the UML kernel for this userspace process. - * - * Return: Always zero, otherwise the current userspace process is ended with non null exit() call - */ +static int stub_exe_fd; + static int userspace_tramp(void *stack) { - struct sigaction sa; - void *addr; - int fd; + char *const argv[] = { "uml-userspace", NULL }; + int pipe_fds[2]; unsigned long long offset; - unsigned long segv_handler = STUB_CODE + - (unsigned long) stub_segv_handler - - (unsigned long) __syscall_stub_start; - - ptrace(PTRACE_TRACEME, 0, 0, 0); - - signal(SIGTERM, SIG_DFL); - signal(SIGWINCH, SIG_IGN); - - fd = phys_mapping(uml_to_phys(__syscall_stub_start), &offset); - addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE, - PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset); - if (addr == MAP_FAILED) { - os_info("mapping mmap stub at 0x%lx failed, errno = %d\n", - STUB_CODE, errno); - exit(1); + struct stub_init_data init_data = { + .stub_start = STUB_START, + .segv_handler = STUB_CODE + + (unsigned long) stub_segv_handler - + (unsigned long) __syscall_stub_start, + }; + struct iomem_region *iomem; + int ret; + + init_data.stub_code_fd = phys_mapping(uml_to_phys(__syscall_stub_start), + &offset); + init_data.stub_code_offset = MMAP_OFFSET(offset); + + init_data.stub_data_fd = phys_mapping(uml_to_phys(stack), &offset); + init_data.stub_data_offset = MMAP_OFFSET(offset); + + /* Set CLOEXEC on all FDs and then unset on all memory related FDs */ + close_range(0, ~0U, CLOSE_RANGE_CLOEXEC); + + fcntl(init_data.stub_data_fd, F_SETFD, 0); + for (iomem = iomem_regions; iomem; iomem = iomem->next) + fcntl(iomem->fd, F_SETFD, 0); + + /* Create a pipe for init_data (no CLOEXEC) and dup2 to STDIN */ + if (pipe(pipe_fds)) + exit(2); + + if (dup2(pipe_fds[0], 0) < 0) + exit(3); + close(pipe_fds[0]); + + /* Write init_data and close write side */ + ret = write(pipe_fds[1], &init_data, sizeof(init_data)); + close(pipe_fds[1]); + + if (ret != sizeof(init_data)) + exit(4); + + execveat(stub_exe_fd, "", argv, NULL, AT_EMPTY_PATH); + + exit(5); +} + +extern char stub_exe_start[]; +extern char stub_exe_end[]; + +extern char *tempdir; + +#define STUB_EXE_NAME_TEMPLATE "/uml-userspace-XXXXXX" + +#ifndef MFD_EXEC +#define MFD_EXEC 0x0010U +#endif + +static int __init init_stub_exe_fd(void) +{ + size_t written = 0; + char *tmpfile = NULL; + + stub_exe_fd = memfd_create("uml-userspace", + MFD_EXEC | MFD_CLOEXEC | MFD_ALLOW_SEALING); + + if (stub_exe_fd < 0) { + printk(UM_KERN_INFO "Could not create executable memfd, using temporary file!"); + + tmpfile = malloc(strlen(tempdir) + + strlen(STUB_EXE_NAME_TEMPLATE) + 1); + if (tmpfile == NULL) + panic("Failed to allocate memory for stub binary name"); + + strcpy(tmpfile, tempdir); + strcat(tmpfile, STUB_EXE_NAME_TEMPLATE); + + stub_exe_fd = mkstemp(tmpfile); + if (stub_exe_fd < 0) + panic("Could not create temporary file for stub binary: %d", + -errno); } - fd = phys_mapping(uml_to_phys(stack), &offset); - addr = mmap((void *) STUB_DATA, - STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_SHARED, fd, offset); - if (addr == MAP_FAILED) { - os_info("mapping segfault stack at 0x%lx failed, errno = %d\n", - STUB_DATA, errno); - exit(1); + while (written < stub_exe_end - stub_exe_start) { + ssize_t res = write(stub_exe_fd, stub_exe_start + written, + stub_exe_end - stub_exe_start - written); + if (res < 0) { + if (errno == EINTR) + continue; + + if (tmpfile) + unlink(tmpfile); + panic("Failed write stub binary: %d", -errno); + } + + written += res; } - set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE); - sigemptyset(&sa.sa_mask); - sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO; - sa.sa_sigaction = (void *) segv_handler; - sa.sa_restorer = NULL; - if (sigaction(SIGSEGV, &sa, NULL) < 0) { - os_info("%s - setting SIGSEGV handler failed - errno = %d\n", - __func__, errno); - exit(1); + if (!tmpfile) { + fcntl(stub_exe_fd, F_ADD_SEALS, + F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL); + } else { + if (fchmod(stub_exe_fd, 00500) < 0) { + unlink(tmpfile); + panic("Could not make stub binary executable: %d", + -errno); + } + + close(stub_exe_fd); + stub_exe_fd = open(tmpfile, O_RDONLY | O_CLOEXEC | O_NOFOLLOW); + if (stub_exe_fd < 0) { + unlink(tmpfile); + panic("Could not reopen stub binary: %d", -errno); + } + + unlink(tmpfile); + free(tmpfile); } - kill(os_getpid(), SIGSTOP); return 0; } +__initcall(init_stub_exe_fd); int userspace_pid[NR_CPUS]; @@ -257,7 +322,7 @@ int start_userspace(unsigned long stub_stack) { void *stack; unsigned long sp; - int pid, status, n, flags, err; + int pid, status, n, err; /* setup a temporary stack page */ stack = mmap(NULL, UM_KERN_PAGE_SIZE, @@ -273,10 +338,10 @@ int start_userspace(unsigned long stub_stack) /* set stack pointer to the end of the stack page, so it can grow downwards */ sp = (unsigned long)stack + UM_KERN_PAGE_SIZE; - flags = CLONE_FILES | SIGCHLD; - /* clone into new userspace process */ - pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack); + pid = clone(userspace_tramp, (void *) sp, + CLONE_VFORK | CLONE_VM | SIGCHLD, + (void *)stub_stack); if (pid < 0) { err = -errno; printk(UM_KERN_ERR "%s : clone failed, errno = %d\n", |