diff options
| author | martin <martin@NetBSD.org> | 2020-03-08 10:22:29 +0000 |
|---|---|---|
| committer | martin <martin@NetBSD.org> | 2020-03-08 10:22:29 +0000 |
| commit | 0c8a29c9016415a08c8f2c8a46efa6082daf1ed1 (patch) | |
| tree | d8eeef11e3799eb655495504ca752c290cf0e914 /libexec | |
| parent | f0d43478d9be6fde780ab31b9fa5e5c9e0f49614 (diff) | |
Pull up following revision(s) (requested by thorpej in ticket #758):
libexec/ld.elf_so/map_object.c: revision 1.61
libexec/ld.elf_so/headers.c: revision 1.68
libexec/ld.elf_so/rtld.c: revision 1.203
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.c | 10 | ||||
| -rw-r--r-- | libexec/ld.elf_so/map_object.c | 9 | ||||
| -rw-r--r-- | libexec/ld.elf_so/rtld.c | 22 |
3 files changed, 27 insertions, 14 deletions
diff --git a/libexec/ld.elf_so/headers.c b/libexec/ld.elf_so/headers.c index efce432d5f7..70e811457b5 100644 --- a/libexec/ld.elf_so/headers.c +++ b/libexec/ld.elf_so/headers.c @@ -1,4 +1,4 @@ -/* $NetBSD: headers.c,v 1.65 2018/12/30 11:55:15 martin Exp $ */ +/* $NetBSD: headers.c,v 1.65.2.1 2020/03/08 10:22:29 martin Exp $ */ /* * Copyright 1996 John D. Polstra. @@ -40,7 +40,7 @@ #include <sys/cdefs.h> #ifndef lint -__RCSID("$NetBSD: headers.c,v 1.65 2018/12/30 11:55:15 martin Exp $"); +__RCSID("$NetBSD: headers.c,v 1.65.2.1 2020/03/08 10:22:29 martin Exp $"); #endif /* not lint */ #include <err.h> @@ -435,9 +435,9 @@ _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..b6c04b7ee6f 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 1.60.2.1 2020/03/08 10:22:29 martin 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 1.60.2.1 2020/03/08 10:22:29 martin 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 7c7308513bc..5367e527384 100644 --- a/libexec/ld.elf_so/rtld.c +++ b/libexec/ld.elf_so/rtld.c @@ -1,4 +1,4 @@ -/* $NetBSD: rtld.c,v 1.197.2.2 2019/12/09 16:12:16 martin Exp $ */ +/* $NetBSD: rtld.c,v 1.197.2.3 2020/03/08 10:22:29 martin Exp $ */ /* * Copyright 1996 John D. Polstra. @@ -40,7 +40,7 @@ #include <sys/cdefs.h> #ifndef lint -__RCSID("$NetBSD: rtld.c,v 1.197.2.2 2019/12/09 16:12:16 martin Exp $"); +__RCSID("$NetBSD: rtld.c,v 1.197.2.3 2020/03/08 10:22:29 martin Exp $"); #endif /* not lint */ #include <sys/param.h> @@ -1771,13 +1771,25 @@ 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; |
