/* * Copyright (c) 1993, David Greenman * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * $Id: kern_exec.c,v 1.45 1996/07/27 03:23:41 dyson Exp $ */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static int *exec_copyout_strings __P((struct image_params *)); static int exec_check_permissions(struct image_params *); /* * XXX trouble here if sizeof(caddr_t) != sizeof(int), other parts * of the sysctl code also assumes this, and sizeof(int) == sizeof(long). */ static struct ps_strings *ps_strings = PS_STRINGS; SYSCTL_INT(_kern, KERN_PS_STRINGS, ps_strings, 0, &ps_strings, 0, ""); static caddr_t usrstack = (caddr_t)USRSTACK; SYSCTL_INT(_kern, KERN_USRSTACK, usrstack, 0, &usrstack, 0, ""); /* * execsw_set is constructed for us by the linker. Each of the items * is a pointer to a `const struct execsw', hence the double pointer here. */ static const struct execsw **execsw = (const struct execsw **)&execsw_set.ls_items[0]; #ifndef _SYS_SYSPROTO_H_ struct execve_args { char *fname; char **argv; char **envv; }; #endif /* * execve() system call. */ int execve(p, uap, retval) struct proc *p; register struct execve_args *uap; int *retval; { struct nameidata nd, *ndp; int *stack_base; int error, len, i; struct image_params image_params, *imgp; struct vattr attr; imgp = &image_params; /* * Initialize part of the common data */ imgp->proc = p; imgp->uap = uap; imgp->attr = &attr; imgp->image_header = NULL; imgp->argc = imgp->envc = 0; imgp->entry_addr = 0; imgp->vmspace_destroyed = 0; imgp->interpreted = 0; imgp->interpreter_name[0] = '\0'; imgp->auxargs = NULL; /* * Allocate temporary demand zeroed space for argument and * environment strings */ imgp->stringbase = (char *)kmem_alloc_wait(exec_map, ARG_MAX); if (imgp->stringbase == NULL) { error = ENOMEM; goto exec_fail; } imgp->stringp = imgp->stringbase; imgp->stringspace = ARG_MAX; /* * Translate the file name. namei() returns a vnode pointer * in ni_vp amoung other things. */ ndp = &nd; NDINIT(ndp, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME, UIO_USERSPACE, uap->fname, p); interpret: error = namei(ndp); if (error) { kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX); goto exec_fail; } imgp->vp = ndp->ni_vp; if (imgp->vp == NULL) { error = ENOEXEC; goto exec_fail_dealloc; } /* * Check file permissions (also 'opens' file) */ error = exec_check_permissions(imgp); /* * Lose the lock on the vnode. It's no longer needed, and must not * exist for the pagefault paging to work below. */ VOP_UNLOCK(imgp->vp); if (error) goto exec_fail_dealloc; /* * Map the image header (first page) of the file into * kernel address space */ error = vm_mmap(exech_map, /* map */ (vm_offset_t *)&imgp->image_header, /* address */ PAGE_SIZE, /* size */ VM_PROT_READ, /* protection */ VM_PROT_READ, /* max protection */ 0, /* flags */ (caddr_t)imgp->vp, /* vnode */ 0); /* offset */ if (error) { uprintf("mmap failed: %d\n",error); goto exec_fail_dealloc; } /* * Loop through list of image activators, calling each one. * If there is no match, the activator returns -1. If there * is a match, but there was an error during the activation, * the error is returned. Otherwise 0 means success. If the * image is interpreted, loop back up and try activating * the interpreter. */ for (i = 0; execsw[i]; ++i) { if (execsw[i]->ex_imgact) error = (*execsw[i]->ex_imgact)(imgp); else continue; if (error == -1) continue; if (error) goto exec_fail_dealloc; if (imgp->interpreted) { /* free old vnode and name buffer */ vrele(ndp->ni_vp); FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI); if (vm_map_remove(exech_map, (vm_offset_t)imgp->image_header, (vm_offset_t)imgp->image_header + PAGE_SIZE)) panic("execve: header dealloc failed (1)"); /* set new name to that of the interpreter */ NDINIT(ndp, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME, UIO_SYSSPACE, imgp->interpreter_name, p); goto interpret; } break; } /* If we made it through all the activators and none matched, exit. */ if (error == -1) { error = ENOEXEC; goto exec_fail_dealloc; } /* * Copy out strings (args and env) and initialize stack base */ stack_base = exec_copyout_strings(imgp); p->p_vmspace->vm_minsaddr = (char *)stack_base; /* * If custom stack fixup routine present for this process * let it do the stack setup. * Else stuff argument count as first item on stack */ if (p->p_sysent->sv_fixup) (*p->p_sysent->sv_fixup)(&stack_base, imgp); else suword(--stack_base, imgp->argc); /* close files on exec */ fdcloseexec(p); /* reset caught signals */ execsigs(p); /* name this process - nameiexec(p, ndp) */ len = min(ndp->ni_cnd.cn_namelen,MAXCOMLEN); bcopy(ndp->ni_cnd.cn_nameptr, p->p_comm, len); p->p_comm[len] = 0; /* * mark as execed, wakeup the process that vforked (if any) and tell * it that it now has it's own resources back */ p->p_flag |= P_EXEC; if (p->p_pptr && (p->p_flag & P_PPWAIT)) { p->p_flag &= ~P_PPWAIT; wakeup((caddr_t)p->p_pptr); } /* * Implement image setuid/setgid. Disallow if the process is * being traced. */ if ((attr.va_mode & (VSUID | VSGID)) && (p->p_flag & P_TRACED) == 0) { /* * Turn off syscall tracing for set-id programs, except for * root. */ if (p->p_tracep && suser(p->p_ucred, &p->p_acflag)) { p->p_traceflag = 0; vrele(p->p_tracep); p->p_tracep = NULL; } /* * Set the new credentials. */ p->p_ucred = crcopy(p->p_ucred); if (attr.va_mode & VSUID) p->p_ucred->cr_uid = attr.va_uid; if (attr.va_mode & VSGID) p->p_ucred->cr_groups[0] = attr.va_gid; p->p_flag |= P_SUGID; } else { p->p_flag &= ~P_SUGID; } /* * Implement correct POSIX saved-id behavior. */ p->p_cred->p_svuid = p->p_ucred->cr_uid; p->p_cred->p_svgid = p->p_ucred->cr_gid; /* * Store the vp for use in procfs */ if (p->p_textvp) /* release old reference */ vrele(p->p_textvp); VREF(ndp->ni_vp); p->p_textvp = ndp->ni_vp; /* * If tracing the process, trap to debugger so breakpoints * can be set before the program executes. */ if (p->p_flag & P_TRACED) psignal(p, SIGTRAP); /* clear "fork but no exec" flag, as we _are_ execing */ p->p_acflag &= ~AFORK; /* Set entry address */ setregs(p, imgp->entry_addr, (u_long)stack_base); /* * free various allocated resources */ kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX); if (vm_map_remove(exech_map, (vm_offset_t)imgp->image_header, (vm_offset_t)imgp->image_header + PAGE_SIZE)) panic("execve: header dealloc failed (2)"); vrele(ndp->ni_vp); FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI); return (0); exec_fail_dealloc: if (imgp->stringbase != NULL) kmem_free_wakeup(exec_map, (vm_offset_t)imgp->stringbase, ARG_MAX); if (imgp->image_header && imgp->image_header != (char *)-1) if (vm_map_remove(exech_map, (vm_offset_t)imgp->image_header, (vm_offset_t)imgp->image_header + PAGE_SIZE)) panic("execve: header dealloc failed (3)"); if (ndp->ni_vp) vrele(ndp->ni_vp); FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI); exec_fail: if (imgp->vmspace_destroyed) { /* sorry, no more process anymore. exit gracefully */ exit1(p, W_EXITCODE(0, SIGABRT)); /* NOT REACHED */ return(0); } else { return(error); } } /* * Destroy old address space, and allocate a new stack * The new stack is only SGROWSIZ large because it is grown * automatically in trap.c. */ int exec_new_vmspace(imgp) struct image_params *imgp; { int error; struct vmspace *vmspace = imgp->proc->p_vmspace; caddr_t stack_addr = (caddr_t) (USRSTACK - SGROWSIZ); imgp->vmspace_destroyed = 1; /* Blow away entire process VM */ if (vmspace->vm_shm) shmexit(imgp->proc); vm_map_remove(&vmspace->vm_map, 0, USRSTACK); /* Allocate a new stack */ error = vm_map_find(&vmspace->vm_map, NULL, 0, (vm_offset_t *)&stack_addr, SGROWSIZ, FALSE, VM_PROT_ALL, VM_PROT_ALL, 0); if (error) return(error); vmspace->vm_ssize = SGROWSIZ >> PAGE_SHIFT; /* Initialize maximum stack address */ vmspace->vm_maxsaddr = (char *)USRSTACK - MAXSSIZ; return(0); } /* * Copy out argument and environment strings from the old process * address space into the temporary string buffer. */ int exec_extract_strings(imgp) struct image_params *imgp; { char **argv, **envv; char *argp, *envp; int error, length; /* * extract arguments first */ argv = imgp->uap->argv; if (argv) { while ((argp = (caddr_t) fuword(argv++))) { if (argp == (caddr_t) -1) return (EFAULT); if ((error = copyinstr(argp, imgp->stringp, imgp->stringspace, &length))) { if (error == ENAMETOOLONG) return(E2BIG); return (error); } imgp->stringspace -= length; imgp->stringp += length; imgp->argc++; } } /* * extract environment strings */ envv = imgp->uap->envv; if (envv) { while ((envp = (caddr_t) fuword(envv++))) { if (envp == (caddr_t) -1) return (EFAULT); if ((error = copyinstr(envp, imgp->stringp, imgp->stringspace, &length))) { if (error == ENAMETOOLONG) return(E2BIG); return (error); } imgp->stringspace -= length; imgp->stringp += length; imgp->envc++; } } return (0); } /* * Copy strings out to the new process address space, constructing * new arg and env vector tables. Return a pointer to the base * so that it can be used as the initial stack pointer. */ int * exec_copyout_strings(imgp) struct image_params *imgp; { int argc, envc; char **vectp; char *stringp, *destp; int *stack_base; struct ps_strings *arginfo; int szsigcode; /* * Calculate string base and vector table pointers. * Also deal with signal trampoline code for this exec type. */ arginfo = PS_STRINGS; szsigcode = *(imgp->proc->p_sysent->sv_szsigcode); destp = (caddr_t)arginfo - szsigcode - SPARE_USRSPACE - roundup((ARG_MAX - imgp->stringspace), sizeof(char *)); /* * install sigcode */ if (szsigcode) copyout(imgp->proc->p_sysent->sv_sigcode, ((caddr_t)arginfo - szsigcode), szsigcode); /* * If we have a valid auxargs ptr, prepare some room * on the stack. */ if (imgp->auxargs) /* * The '+ 2' is for the null pointers at the end of each of the * arg and env vector sets, and 'AT_COUNT*2' is room for the * ELF Auxargs data. */ vectp = (char **)(destp - (imgp->argc + imgp->envc + 2 + AT_COUNT*2) * sizeof(char*)); else /* * The '+ 2' is for the null pointers at the end of each of the * arg and env vector sets */ vectp = (char **) (destp - (imgp->argc + imgp->envc + 2) * sizeof(char*)); /* * vectp also becomes our initial stack base */ stack_base = (int *)vectp; stringp = imgp->stringbase; argc = imgp->argc; envc = imgp->envc; /* * Copy out strings - arguments and environment. */ copyout(stringp, destp, ARG_MAX - imgp->stringspace); /* * Fill in "ps_strings" struct for ps, w, etc. */ suword(&arginfo->ps_argvstr, (int)vectp); suword(&arginfo->ps_nargvstr, argc); /* * Fill in argument portion of vector table. */ for (; argc > 0; --argc) { suword(vectp++, (int)destp); while (*stringp++ != 0) destp++; destp++; } /* a null vector table pointer seperates the argp's from the envp's */ suword(vectp++, 0); suword(&arginfo->ps_envstr, (int)vectp); suword(&arginfo->ps_nenvstr, envc); /* * Fill in environment portion of vector table. */ for (; envc > 0; --envc) { suword(vectp++, (int)destp); while (*stringp++ != 0) destp++; destp++; } /* end of vector table is a null pointer */ suword(vectp, 0); return (stack_base); } /* * Check permissions of file to execute. * Return 0 for success or error code on failure. */ static int exec_check_permissions(imgp) struct image_params *imgp; { struct proc *p = imgp->proc; struct vnode *vp = imgp->vp; struct vattr *attr = imgp->attr; int error; /* * Check number of open-for-writes on the file and deny execution * if there are any. */ if (vp->v_writecount) { return (ETXTBSY); } /* Get file attributes */ error = VOP_GETATTR(vp, attr, p->p_ucred, p); if (error) return (error); /* * 1) Check if file execution is disabled for the filesystem that this * file resides on. * 2) Insure that at least one execute bit is on - otherwise root * will always succeed, and we don't want to happen unless the * file really is executable. * 3) Insure that the file is a regular file. */ if ((vp->v_mount->mnt_flag & MNT_NOEXEC) || ((attr->va_mode & 0111) == 0) || (attr->va_type != VREG)) { return (EACCES); } /* * Zero length files can't be exec'd */ if (attr->va_size == 0) return (ENOEXEC); /* * Disable setuid/setgid if the filesystem prohibits it or if * the process is being traced. */ if ((vp->v_mount->mnt_flag & MNT_NOSUID) || (p->p_flag & P_TRACED)) attr->va_mode &= ~(VSUID | VSGID); /* * Check for execute permission to file based on current credentials. * Then call filesystem specific open routine (which does nothing * in the general case). */ error = VOP_ACCESS(vp, VEXEC, p->p_ucred, p); if (error) return (error); error = VOP_OPEN(vp, FREAD, p->p_ucred, p); if (error) return (error); return (0); }