library_mquery.c

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Author : bluhm
Date : 2019-12-09 23:15:03
Hash : f7d771ca
Message : When loading a library, mmap(2) may fail. Then everything gets unmapped and ld.so tries again with different random address layout. In this case, use the new libc executable address for msyscall(2), not one from the first try. Fixes sporadic bogus syscall on i386. OK deraadt@
libexec/ld.so/library_mquery.c
/*	$OpenBSD: library_mquery.c,v 1.64 2019/12/09 23:15:03 bluhm Exp $ */

/*
 * Copyright (c) 2002 Dale Rahn
 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
 *
 * 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 ``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 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.
 *
 */

#define _DYN_LOADER

#include <sys/types.h>
#include <fcntl.h>
#include <sys/mman.h>

#include "syscall.h"
#include "archdep.h"
#include "resolve.h"
#include "sod.h"

#define PFLAGS(X) ((((X) & PF_R) ? PROT_READ : 0) | \
		   (((X) & PF_W) ? PROT_WRITE : 0) | \
		   (((X) & PF_X) ? PROT_EXEC : 0))

void
_dl_load_list_free(struct load_list *load_list)
{
	struct load_list *next;
	Elf_Addr align = _dl_pagesz - 1;

	while (load_list != NULL) {
		if (load_list->start != NULL)
			_dl_munmap(load_list->start,
			    ((load_list->size) + align) & ~align);
		next = load_list->next;
		_dl_free(load_list);
		load_list = next;
	}
}


void
_dl_unload_shlib(elf_object_t *object)
{
	struct dep_node *n;
	elf_object_t *load_object = object->load_object;

	/*
	 * If our load object has become unreferenced then we lost the
	 * last group reference to it, so the entire group should be taken
	 * down.  The current object is somewhere below load_object in
	 * the child_vec tree, so it'll get cleaned up by the recursion.
	 * That means we can just switch here to the load object.
	 */
	if (load_object != object && OBJECT_REF_CNT(load_object) == 0 &&
	    (load_object->status & STAT_UNLOADED) == 0) {
		DL_DEB(("unload_shlib switched from %s to %s\n",
		    object->load_name, load_object->load_name));
		object = load_object;
		goto unload;
	}

	DL_DEB(("unload_shlib called on %s\n", object->load_name));
	if (OBJECT_REF_CNT(object) == 0 &&
	    (object->status & STAT_UNLOADED) == 0) {
		struct object_vector vec;
		int i;
unload:
		object->status |= STAT_UNLOADED;
		for (vec = object->child_vec, i = 0; i < vec.len; i++)
			_dl_unload_shlib(vec.vec[i]);
		TAILQ_FOREACH(n, &object->grpref_list, next_sib)
			_dl_unload_shlib(n->data);
		DL_DEB(("unload_shlib unloading on %s\n", object->load_name));
		_dl_load_list_free(object->load_list);
		_dl_remove_object(object);
	}
}


elf_object_t *
_dl_tryload_shlib(const char *libname, int type, int flags)
{
	int libfile, i;
	struct load_list *ld, *lowld = NULL;
	elf_object_t *object;
	Elf_Dyn *dynp = NULL;
	Elf_Ehdr *ehdr;
	Elf_Phdr *phdp;
	Elf_Addr load_end = 0;
	Elf_Addr align = _dl_pagesz - 1, off, size;
	Elf_Phdr *ptls = NULL;
	Elf_Addr relro_addr = 0, relro_size = 0;
	struct stat sb;
	char hbuf[4096], *exec_start;
	size_t exec_size;

#define ROUND_PG(x) (((x) + align) & ~(align))
#define TRUNC_PG(x) ((x) & ~(align))

	libfile = _dl_open(libname, O_RDONLY | O_CLOEXEC);
	if (libfile < 0) {
		_dl_errno = DL_CANT_OPEN;
		return(0);
	}

	if ( _dl_fstat(libfile, &sb) < 0) {
		_dl_errno = DL_CANT_OPEN;
		return(0);
	}

	for (object = _dl_objects; object != NULL; object = object->next) {
		if (object->dev == sb.st_dev &&
		    object->inode == sb.st_ino) {
			object->obj_flags |= flags & DF_1_GLOBAL;
			_dl_close(libfile);
			if (_dl_loading_object == NULL)
				_dl_loading_object = object;
			if (object->load_object != _dl_objects &&
			    object->load_object != _dl_loading_object) {
				_dl_link_grpref(object->load_object,
				    _dl_loading_object);
			}
			return(object);
		}
	}

	_dl_read(libfile, hbuf, sizeof(hbuf));
	ehdr = (Elf_Ehdr *)hbuf;
	if (ehdr->e_ident[0] != ELFMAG0  || ehdr->e_ident[1] != ELFMAG1 ||
	    ehdr->e_ident[2] != ELFMAG2 || ehdr->e_ident[3] != ELFMAG3 ||
	    ehdr->e_type != ET_DYN || ehdr->e_machine != MACHID) {
		_dl_close(libfile);
		_dl_errno = DL_NOT_ELF;
		return(0);
	}

	/* Insertion sort */
#define LDLIST_INSERT(ld) do { \
	struct load_list **_ld; \
	for (_ld = &lowld; *_ld != NULL; _ld = &(*_ld)->next) \
		if ((*_ld)->moff > ld->moff) \
			break; \
	ld->next = *_ld; \
	*_ld = ld; \
} while (0)
	/*
	 *  Alright, we might have a winner!
	 *  Figure out how much VM space we need and set up the load
	 *  list that we'll use to find free VM space.
	 */
	phdp = (Elf_Phdr *)(hbuf + ehdr->e_phoff);
	for (i = 0; i < ehdr->e_phnum; i++, phdp++) {
		switch (phdp->p_type) {
		case PT_LOAD:
			off = (phdp->p_vaddr & align);
			size = off + phdp->p_filesz;

			if (size != 0) {
				ld = _dl_malloc(sizeof(struct load_list));
				if (ld == NULL)
					_dl_oom();
				ld->start = NULL;
				ld->size = size;
				ld->moff = TRUNC_PG(phdp->p_vaddr);
				ld->foff = TRUNC_PG(phdp->p_offset);
				ld->prot = PFLAGS(phdp->p_flags);
				LDLIST_INSERT(ld);
			}

			if ((PFLAGS(phdp->p_flags) & PROT_WRITE) == 0 ||
			    ROUND_PG(size) == ROUND_PG(off + phdp->p_memsz))
				break;
			/* This phdr has a zfod section */
			ld = _dl_calloc(1, sizeof(struct load_list));
			if (ld == NULL)
				_dl_oom();
			ld->start = NULL;
			ld->size = ROUND_PG(off + phdp->p_memsz) -
			    ROUND_PG(size);
			ld->moff = TRUNC_PG(phdp->p_vaddr) +
			    ROUND_PG(size);
			ld->foff = -1;
			ld->prot = PFLAGS(phdp->p_flags);
			LDLIST_INSERT(ld);
			break;
		case PT_DYNAMIC:
			dynp = (Elf_Dyn *)phdp->p_vaddr;
			break;
		case PT_TLS:
			if (phdp->p_filesz > phdp->p_memsz) {
				_dl_printf("%s: invalid tls data in %s.\n",
				    __progname, libname);
				_dl_close(libfile);
				_dl_errno = DL_CANT_LOAD_OBJ;
				return(0);
			}
			if (!_dl_tib_static_done) {
				ptls = phdp;
				break;
			}
			_dl_printf("%s: unsupported TLS program header in %s\n",
			    __progname, libname);
			_dl_close(libfile);
			_dl_errno = DL_CANT_LOAD_OBJ;
			return(0);
		default:
			break;
		}
	}

#define LOFF ((Elf_Addr)lowld->start - lowld->moff)

retry:
	exec_start = NULL;
	exec_size = 0;
	for (ld = lowld; ld != NULL; ld = ld->next) {
		off_t foff;
		int fd, flags;
		void *res;

		flags = MAP_PRIVATE;

		if (ld->foff < 0) {
			fd = -1;
			foff = 0;
			flags |= MAP_ANON;
		} else {
			fd = libfile;
			foff = ld->foff;
		}

		if (ld == lowld) {
			/*
			 * Add PROT_EXEC to force the first allocation in
			 * EXEC region unless it is writable.
			 */
			int exec = (ld->prot & PROT_WRITE) ? 0 : PROT_EXEC;
			res = _dl_mquery((void *)(LOFF + ld->moff),
			    ROUND_PG(ld->size), ld->prot | exec, flags,
			    fd, foff);
			if (_dl_mmap_error(res))
				goto fail;
			lowld->start = res;
		}

		res = _dl_mmap((void *)(LOFF + ld->moff), ROUND_PG(ld->size),
		    ld->prot, flags | MAP_FIXED | __MAP_NOREPLACE, fd, foff);
		if (_dl_mmap_error(res)) {
			struct load_list *ll;

			/* Unmap any mappings that we did get in. */
			for (ll = lowld; ll != NULL && ll != ld;
			     ll = ll->next) {
				_dl_munmap(ll->start, ROUND_PG(ll->size));
			}

			lowld->start += ROUND_PG(ld->size);
			goto retry;
		}

		if ((ld->prot & PROT_EXEC) && exec_start == NULL) {
			exec_start = (void *)(LOFF + ld->moff);
			exec_size = ROUND_PG(ld->size);
		}

		ld->start = res;
	}

	for (ld = lowld; ld != NULL; ld = ld->next) {
		/* Zero out everything past the EOF */
		if ((ld->prot & PROT_WRITE) != 0 && (ld->size & align) != 0)
			_dl_memset((char *)ld->start + ld->size, 0,
			    _dl_pagesz - (ld->size & align));
		load_end = (Elf_Addr)ld->start + ROUND_PG(ld->size);
	}

	phdp = (Elf_Phdr *)(hbuf + ehdr->e_phoff);
	for (i = 0; i < ehdr->e_phnum; i++, phdp++) {
		if (phdp->p_type == PT_OPENBSD_RANDOMIZE)
			_dl_arc4randombuf((char *)(phdp->p_vaddr + LOFF),
			    phdp->p_memsz);
		else if (phdp->p_type == PT_GNU_RELRO) {
			relro_addr = phdp->p_vaddr + LOFF;
			relro_size = phdp->p_memsz;
		}
	}

	_dl_close(libfile);

	dynp = (Elf_Dyn *)((unsigned long)dynp + LOFF);
	object = _dl_finalize_object(libname, dynp,
	    (Elf_Phdr *)((char *)lowld->start + ehdr->e_phoff), ehdr->e_phnum,
	    type, (Elf_Addr)lowld->start, LOFF);
	if (object) {
		char *soname = (char *)object->Dyn.info[DT_SONAME];

		object->load_size = (Elf_Addr)load_end - (Elf_Addr)lowld->start;
		object->load_list = lowld;
		/* set inode, dev from stat info */
		object->dev = sb.st_dev;
		object->inode = sb.st_ino;
		object->obj_flags |= flags;
		object->relro_addr = relro_addr;
		object->relro_size = relro_size;
		_dl_set_sod(object->load_name, &object->sod);
		if (ptls != NULL && ptls->p_memsz)
			_dl_set_tls(object, ptls, (Elf_Addr)lowld->start,
			    libname);

		/* Request permission for system calls in libc.so's text segment */
		if (soname != NULL &&
		    _dl_strncmp(soname, "libc.so.", 8) == 0) {
			if (_dl_msyscall(exec_start, exec_size) == -1)
				_dl_printf("msyscall %lx %lx error\n",
				    exec_start, exec_size);
		}
	} else {
		_dl_load_list_free(lowld);
	}
	return(object);
fail:
	_dl_printf("%s: ld.so mmap failed mapping %s.\n", __progname, libname);
	_dl_close(libfile);
	_dl_errno = DL_CANT_MMAP;
	_dl_load_list_free(lowld);
	return(0);
}
IABSD.fr/src/libexec/ld.so/library_mquery.c

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IABSD.fr/src /libexec/ld.so/library_mquery.c
