Do not stack-protect ifunc resolvers [BZ #7065]

When dynamically linking, ifunc resolvers are called before TLS is
initialized, so they cannot be safely stack-protected.

We avoid disabling stack-protection on large numbers of files by
using __attribute__ ((__optimize__ ("-fno-stack-protector")))
to turn it off just for the resolvers themselves.  (We provide
the attribute even when statically linking, because we will later
use it elsewhere too.)
This commit is contained in:
Nick Alcock 2016-12-26 10:08:41 +01:00 committed by Florian Weimer
parent 003a27e819
commit de6591238b
16 changed files with 62 additions and 1 deletions

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@ -1,3 +1,28 @@
2016-12-26 Nick Alcock <nick.alcock@oracle.com>
[BZ #7065]
* configure.ac (HAVE_CC_NO_STACK_PROTECTOR): Define.
* config.h.in (HAVE_CC_NO_STACK_PROTECTOR): New macro.
* include/libc-symbols.h (inhibit_stack_protector): New macro.
(__ifunc_resolver): Use it.
* elf/ifuncdep2.c (foo1_ifunc, foo2_ifunc, foo3_ifunc): Apply
inhibit_stack_protector.
* elf/ifuncmain6pie.c (foo_ifunc): Likewise.
* elf/ifuncmain7.c (foo_ifunc): Likewise.
* elf/ifuncmod1.c (foo_ifunc, foo_hidden_ifunc)
(foo_protected_ifunc): Likewise.
* elf/ifuncmod5.c (foo_ifunc, foo_hidden_ifunc)
(foo_protected_ifunc): Likewise.
* sysdeps/generic/ifunc-sel.h (ifunc_sel, ifunc_one): Likewise.
* sysdeps/nacl/nacl_interface_query.c
(nacl_interface_query_ifunc): Likewise.
* sysdeps/powerpc/ifunc-sel.h (ifunc_sel, ifunc_one): Likewise.
* sysdeps/unix/sysv/linux/x86_64/x32/getcpu.c (getcpu_ifunc):
Likewise.
* sysdeps/x86_64/ifuncmod8.c (foo_ifunc): Likewise.
* sysdeps/unix/make-syscalls.sh: Apply inhibit_stack_protector to
the generated vDSO syscall resolver.
2016-12-26 Nick Alcock <nick.alcock@oracle.com>
Florian Weimer <fweimer@redhat.com>

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@ -48,6 +48,10 @@
/* Define if compiler accepts -ftree-loop-distribute-patterns. */
#undef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
/* Define if compiler accepts -fno-stack-protector in an
__attribute__ ((__optimize__)). */
#undef HAVE_CC_NO_STACK_PROTECTOR
/* The level of stack protection in use for glibc as a whole.
May be overridden on a file-by-file basis. */
#ifndef STACK_PROTECTOR_LEVEL

2
configure vendored
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@ -3994,6 +3994,8 @@ stack_protector=
no_stack_protector=
if test "$libc_cv_ssp" = yes; then
no_stack_protector="-fno-stack-protector -DSTACK_PROTECTOR_LEVEL=0"
$as_echo "#define HAVE_CC_NO_STACK_PROTECTOR 1" >>confdefs.h
fi
if test "$enable_stack_protector" = yes && test "$libc_cv_ssp" = yes; then

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@ -653,6 +653,7 @@ stack_protector=
no_stack_protector=
if test "$libc_cv_ssp" = yes; then
no_stack_protector="-fno-stack-protector -DSTACK_PROTECTOR_LEVEL=0"
AC_DEFINE(HAVE_CC_NO_STACK_PROTECTOR)
fi
if test "$enable_stack_protector" = yes && test "$libc_cv_ssp" = yes; then

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@ -32,6 +32,7 @@ void * foo1_ifunc (void) __asm__ ("foo1");
__asm__(".type foo1, %gnu_indirect_function");
void *
inhibit_stack_protector
foo1_ifunc (void)
{
return ifunc_sel (one, minus_one, zero);
@ -41,6 +42,7 @@ void * foo2_ifunc (void) __asm__ ("foo2");
__asm__(".type foo2, %gnu_indirect_function");
void *
inhibit_stack_protector
foo2_ifunc (void)
{
return ifunc_sel (minus_one, one, zero);
@ -50,6 +52,7 @@ void * foo3_ifunc (void) __asm__ ("foo3");
__asm__(".type foo3, %gnu_indirect_function");
void *
inhibit_stack_protector
foo3_ifunc (void)
{
return ifunc_sel (one, zero, minus_one);

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@ -21,6 +21,7 @@ void * foo_ifunc (void) __asm__ ("foo");
__asm__(".type foo, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_ifunc (void)
{
return ifunc_one (one);

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@ -20,6 +20,7 @@ __asm__(".type foo, %gnu_indirect_function");
static void *
__attribute__ ((used))
inhibit_stack_protector
foo_ifunc (void)
{
return ifunc_one (one);

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@ -36,6 +36,7 @@ void * foo_ifunc (void) __asm__ ("foo");
__asm__(".type foo, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_ifunc (void)
{
return ifunc_sel (one, minus_one, zero);
@ -45,6 +46,7 @@ void * foo_hidden_ifunc (void) __asm__ ("foo_hidden");
__asm__(".type foo_hidden, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_hidden_ifunc (void)
{
return ifunc_sel (minus_one, one, zero);
@ -54,6 +56,7 @@ void * foo_protected_ifunc (void) __asm__ ("foo_protected");
__asm__(".type foo_protected, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_protected_ifunc (void)
{
return ifunc_sel (one, zero, minus_one);

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@ -31,6 +31,7 @@ void * foo_ifunc (void) __asm__ ("foo");
__asm__(".type foo, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_ifunc (void)
{
return ifunc_sel (one, minus_one, zero);
@ -40,6 +41,7 @@ void * foo_hidden_ifunc (void) __asm__ ("foo_hidden");
__asm__(".type foo_hidden, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_hidden_ifunc (void)
{
return ifunc_sel (minus_one, one, zero);
@ -49,6 +51,7 @@ void * foo_protected_ifunc (void) __asm__ ("foo_protected");
__asm__(".type foo_protected, %gnu_indirect_function");
void *
inhibit_stack_protector
foo_protected_ifunc (void)
{
return ifunc_sel (one, zero, minus_one);

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@ -336,6 +336,16 @@ for linking")
#define attribute_relro __attribute__ ((section (".data.rel.ro")))
/* Used to disable stack protection in sensitive places, like ifunc
resolvers and early static TLS init. */
#ifdef HAVE_CC_NO_STACK_PROTECTOR
# define inhibit_stack_protector \
__attribute__ ((__optimize__ ("-fno-stack-protector")))
#else
# define inhibit_stack_protector
#endif
/* The following macros are used for PLT bypassing within libc.so
(and if needed other libraries similarly).
First of all, you need to have the function prototyped somewhere,
@ -737,7 +747,7 @@ for linking")
/* Helper / base macros for indirect function symbols. */
#define __ifunc_resolver(type_name, name, expr, arg, init, classifier) \
classifier void *name##_ifunc (arg) \
classifier inhibit_stack_protector void *name##_ifunc (arg) \
{ \
init (); \
__typeof (type_name) *res = expr; \

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@ -5,6 +5,7 @@
extern int global;
static inline void *
inhibit_stack_protector
ifunc_sel (int (*f1) (void), int (*f2) (void), int (*f3) (void))
{
switch (global)
@ -19,6 +20,7 @@ ifunc_sel (int (*f1) (void), int (*f2) (void), int (*f3) (void))
}
static inline void *
inhibit_stack_protector
ifunc_one (int (*f1) (void))
{
return f1;

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@ -29,6 +29,7 @@ extern TYPE_nacl_irt_query nacl_interface_query_ifunc (void)
asm ("nacl_interface_query");
TYPE_nacl_irt_query
inhibit_stack_protector
nacl_interface_query_ifunc (void)
{
return &__nacl_irt_query;

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@ -5,6 +5,7 @@
extern int global;
static inline void *
inhibit_stack_protector
ifunc_sel (int (*f1) (void), int (*f2) (void), int (*f3) (void))
{
register void *ret __asm__ ("r3");
@ -32,6 +33,7 @@ ifunc_sel (int (*f1) (void), int (*f2) (void), int (*f3) (void))
}
static inline void *
inhibit_stack_protector
ifunc_one (int (*f1) (void))
{
register void *ret __asm__ ("r3");

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@ -287,6 +287,7 @@ while read file srcfile caller syscall args strong weak; do
(echo '#include <dl-vdso.h>'; \\
echo 'extern void *${strong}_ifunc (void) __asm ("${strong}");'; \\
echo 'void *'; \\
echo 'inhibit_stack_protector'; \\
echo '${strong}_ifunc (void)'; \\
echo '{'; \\
echo ' PREPARE_VERSION_KNOWN (symver, ${vdso_symver});'; \\

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@ -21,6 +21,7 @@
void *getcpu_ifunc (void) __asm__ ("__getcpu");
void *
inhibit_stack_protector
getcpu_ifunc (void)
{
PREPARE_VERSION (linux26, "LINUX_2.6", 61765110);

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@ -28,6 +28,7 @@ foo_impl (float x)
}
void *
inhibit_stack_protector
foo_ifunc (void)
{
__m128i xmm = _mm_set1_epi32 (-1);