From 7fd852f860b047f0e540360760aa4c95fd9285b2 Mon Sep 17 00:00:00 2001 From: Maxim Sobolev Date: Sat, 30 Jan 2016 04:16:05 +0000 Subject: [PATCH] This seems like a very trivial bug that should have been squashed a long time ago, but for some reason it was not. Basically, without this change dlopen(3)'ing an empty .so file would just cause application to dump core with SIGSEGV. Make sure the file has enough data for at least the ELF header before mmap'ing it. Add a test case to check that dlopen an empty file return an error. There were a separate discussion as to whether it should be SIGBUS instead when you try to access region mapped from an empty file, but it's definitely SIGSEGV now, so if anyone want to check that please be my guest. Reviewed by: mjg, cem MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D5112 --- lib/libc/tests/gen/Makefile | 1 + lib/libc/tests/gen/dlopen_empty_test.c | 97 ++++++++++++++++++++++++++ libexec/rtld-elf/map_object.c | 12 +++- 3 files changed, 107 insertions(+), 3 deletions(-) create mode 100644 lib/libc/tests/gen/dlopen_empty_test.c diff --git a/lib/libc/tests/gen/Makefile b/lib/libc/tests/gen/Makefile index b700312d8128..083097730cc0 100644 --- a/lib/libc/tests/gen/Makefile +++ b/lib/libc/tests/gen/Makefile @@ -11,6 +11,7 @@ ATF_TESTS_C+= ftw_test ATF_TESTS_C+= popen_test ATF_TESTS_C+= posix_spawn_test ATF_TESTS_C+= wordexp_test +ATF_TESTS_C+= dlopen_empty_test # TODO: t_closefrom, t_cpuset, t_fmtcheck, t_randomid, t_sleep # TODO: t_siginfo (fixes require further inspection) diff --git a/lib/libc/tests/gen/dlopen_empty_test.c b/lib/libc/tests/gen/dlopen_empty_test.c new file mode 100644 index 000000000000..42f9269a10b2 --- /dev/null +++ b/lib/libc/tests/gen/dlopen_empty_test.c @@ -0,0 +1,97 @@ +/*- + * Copyright (c) 2016 Maksym Sobolyev + * 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. + */ + +#include +__FBSDID("$FreeBSD$"); + +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +static const char *funname; +static char *soname; + +static void +sigsegv_handler(int sig __unused) +{ + unlink(soname); + free(soname); + atf_tc_fail("got SIGSEGV in the %s(3)", funname); +} + +ATF_TC(dlopen_empty_test); +ATF_TC_HEAD(dlopen_empty_test, tc) +{ + atf_tc_set_md_var(tc, "descr", "Tests the dlopen() of an empty file " + "returns an error"); +} +ATF_TC_BODY(dlopen_empty_test, tc) +{ + char tempname[] = "/tmp/temp.XXXXXX"; + char *fname; + int fd; + void *dlh; + struct sigaction act, oact; + + fname = mktemp(tempname); + ATF_REQUIRE_MSG(fname != NULL, "mktemp failed; errno=%d", errno); + asprintf(&soname, "%s.so", fname); + ATF_REQUIRE_MSG(soname != NULL, "asprintf failed; errno=%d", ENOMEM); + fd = open(soname, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE); + ATF_REQUIRE_MSG(fd != -1, "open(\"%s\") failed; errno=%d", soname, errno); + close(fd); + + act.sa_handler = sigsegv_handler; + act.sa_flags = 0; + sigemptyset(&act.sa_mask); + ATF_CHECK_MSG(sigaction(SIGSEGV, &act, &oact) != -1, + "sigaction() failed"); + + funname = "dlopen"; + dlh = dlopen(soname, RTLD_LAZY); + if (dlh != NULL) { + funname = "dlclose"; + dlclose(dlh); + } + ATF_REQUIRE_MSG(dlh == NULL, "dlopen(\"%s\") did not fail", soname); + unlink(soname); + free(soname); +} + +ATF_TP_ADD_TCS(tp) +{ + + ATF_TP_ADD_TC(tp, dlopen_empty_test); + + return (atf_no_error()); +} diff --git a/libexec/rtld-elf/map_object.c b/libexec/rtld-elf/map_object.c index 6012015bcc28..f4f6f4221816 100644 --- a/libexec/rtld-elf/map_object.c +++ b/libexec/rtld-elf/map_object.c @@ -38,7 +38,7 @@ #include "debug.h" #include "rtld.h" -static Elf_Ehdr *get_elf_header(int, const char *); +static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *); static int convert_prot(int); /* Elf flags -> mmap protection */ static int convert_flags(int); /* Elf flags -> mmap flags */ @@ -91,7 +91,7 @@ map_object(int fd, const char *path, const struct stat *sb) char *note_map; size_t note_map_len; - hdr = get_elf_header(fd, path); + hdr = get_elf_header(fd, path, sb); if (hdr == NULL) return (NULL); @@ -324,10 +324,16 @@ map_object(int fd, const char *path, const struct stat *sb) } static Elf_Ehdr * -get_elf_header(int fd, const char *path) +get_elf_header(int fd, const char *path, const struct stat *sbp) { Elf_Ehdr *hdr; + /* Make sure file has enough data for the ELF header */ + if (sbp != NULL && sbp->st_size < sizeof(Elf_Ehdr)) { + _rtld_error("%s: invalid file format", path); + return (NULL); + } + hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, fd, 0); if (hdr == (Elf_Ehdr *)MAP_FAILED) {