summaryrefslogtreecommitdiff
path: root/libexec
diff options
context:
space:
mode:
authorthorpej <thorpej@NetBSD.org>2020-03-04 01:21:17 +0000
committerthorpej <thorpej@NetBSD.org>2020-03-04 01:21:17 +0000
commit7b5cd1c22749e34a84fcbc1e5a6dab8d028dfae6 (patch)
treed5c611406ca43d09a5ad8e841091cbe2b94e39d8 /libexec
parentbe187b29b9033202a9074911afe582e9dff2de5c (diff)
PT_GNU_RELRO segments are arranged such that their vaddr + memsz ends
on a linker common page size boundary. However, if the common page size used by the linker is less than the VM page size being used by the kernel, this can end up in the middle of a VM page and when the region is write- protected, this can cause objects in neighboring .data to get incorrectly write-protected, resulting in a crash. Avoid this situation by calculating the end of the RELRO region not by rounding memsz up to the VM page size, but rather by adding vaddr + memsz and then truncating to the VM page size. Fixes PR toolchain/55043. XXX pullup-9
Diffstat (limited to 'libexec')
-rw-r--r--libexec/ld.elf_so/headers.c10
-rw-r--r--libexec/ld.elf_so/map_object.c9
-rw-r--r--libexec/ld.elf_so/rtld.c22
3 files changed, 27 insertions, 14 deletions
diff --git a/libexec/ld.elf_so/headers.c b/libexec/ld.elf_so/headers.c
index fe1bc956a83..6bfba553303 100644
--- a/libexec/ld.elf_so/headers.c
+++ b/libexec/ld.elf_so/headers.c
@@ -1,4 +1,4 @@
-/* $NetBSD: headers.c,v 1.67 2020/02/29 18:53:55 kamil Exp $ */
+/* $NetBSD: headers.c,v 1.68 2020/03/04 01:21:17 thorpej Exp $ */
/*
* Copyright 1996 John D. Polstra.
@@ -40,7 +40,7 @@
#include <sys/cdefs.h>
#ifndef lint
-__RCSID("$NetBSD: headers.c,v 1.67 2020/02/29 18:53:55 kamil Exp $");
+__RCSID("$NetBSD: headers.c,v 1.68 2020/03/04 01:21:17 thorpej Exp $");
#endif /* not lint */
#include <err.h>
@@ -516,9 +516,9 @@ _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry)
#ifdef GNU_RELRO
case PT_GNU_RELRO:
- obj->relro_page = obj->relocbase
- + round_down(ph->p_vaddr);
- obj->relro_size = round_up(ph->p_memsz);
+ /* rounding happens later. */
+ obj->relro_page = obj->relocbase + ph->p_vaddr;
+ obj->relro_size = ph->p_memsz;
dbg(("headers: %s %p phsize %" PRImemsz,
"PT_GNU_RELRO", (void *)(uintptr_t)vaddr,
ph->p_memsz));
diff --git a/libexec/ld.elf_so/map_object.c b/libexec/ld.elf_so/map_object.c
index 14afb4a6c92..0416df8c8c9 100644
--- a/libexec/ld.elf_so/map_object.c
+++ b/libexec/ld.elf_so/map_object.c
@@ -1,4 +1,4 @@
-/* $NetBSD: map_object.c,v 1.60 2019/01/06 19:44:54 joerg Exp $ */
+/* $NetBSD: map_object.c,v 1.61 2020/03/04 01:21:17 thorpej Exp $ */
/*
* Copyright 1996 John D. Polstra.
@@ -34,7 +34,7 @@
#include <sys/cdefs.h>
#ifndef lint
-__RCSID("$NetBSD: map_object.c,v 1.60 2019/01/06 19:44:54 joerg Exp $");
+__RCSID("$NetBSD: map_object.c,v 1.61 2020/03/04 01:21:17 thorpej Exp $");
#endif /* not lint */
#include <errno.h>
@@ -406,8 +406,9 @@ _rtld_map_object(const char *path, int fd, const struct stat *sb)
obj->relocbase = mapbase - base_vaddr;
#ifdef GNU_RELRO
- obj->relro_page = obj->relocbase + round_down(relro_page);
- obj->relro_size = round_up(relro_size);
+ /* rounding happens later. */
+ obj->relro_page = obj->relocbase + relro_page;
+ obj->relro_size = relro_size;
#endif
if (obj->dynamic)
diff --git a/libexec/ld.elf_so/rtld.c b/libexec/ld.elf_so/rtld.c
index 732a3c51e09..888977a3907 100644
--- a/libexec/ld.elf_so/rtld.c
+++ b/libexec/ld.elf_so/rtld.c
@@ -1,4 +1,4 @@
-/* $NetBSD: rtld.c,v 1.202 2020/02/29 04:23:05 kamil Exp $ */
+/* $NetBSD: rtld.c,v 1.203 2020/03/04 01:21:17 thorpej Exp $ */
/*
* Copyright 1996 John D. Polstra.
@@ -40,7 +40,7 @@
#include <sys/cdefs.h>
#ifndef lint
-__RCSID("$NetBSD: rtld.c,v 1.202 2020/02/29 04:23:05 kamil Exp $");
+__RCSID("$NetBSD: rtld.c,v 1.203 2020/03/04 01:21:17 thorpej Exp $");
#endif /* not lint */
#include <sys/param.h>
@@ -1773,13 +1773,25 @@ int
_rtld_relro(const Obj_Entry *obj, bool wantmain)
{
#ifdef GNU_RELRO
- if (obj->relro_size == 0)
+ /*
+ * If our VM page size is larger than the page size used by the
+ * linker when laying out the object, we could end up making data
+ * read-only that is unintended. Detect and avoid this situation.
+ * It may mean we are unable to protect everything we'd like, but
+ * it's better than crashing.
+ */
+ uintptr_t relro_end = (uintptr_t)obj->relro_page + obj->relro_size;
+ uintptr_t relro_start = round_down((uintptr_t)obj->relro_page);
+ assert(relro_end >= relro_start);
+ size_t relro_size = round_down(relro_end) - relro_start;
+
+ if (relro_size == 0)
return 0;
if (wantmain != (obj ==_rtld_objmain))
return 0;
- dbg(("RELRO %s %p %zx\n", obj->path, obj->relro_page, obj->relro_size));
- if (mprotect(obj->relro_page, obj->relro_size, PROT_READ) == -1) {
+ dbg(("RELRO %s %p %zx\n", obj->path, (void *)relro_start, relro_size));
+ if (mprotect((void *)relro_start, relro_size, PROT_READ) == -1) {
_rtld_error("%s: Cannot enforce relro " "protection: %s",
obj->path, xstrerror(errno));
return -1;