Carefully update stack guard bytes inside __guard_setup().
This is necessary to make sure that functions that can have stack protection are not used to update the stack guard. If not, the stack guard check would fail when it shouldn't. guard_setup() calls elf_aux_info(), which, in turn, calls memcpy() to update stack_chk_guard. If either elf_aux_info() or memcpy() have stack protection enabled, __stack_chk_guard will be modified before returning from them, causing the stack protection check to fail. This change uses a temporary buffer to delay changing __stack_chk_guard until elf_aux_info() returns. Submitted by: Luis Pires MFC after: 1 week Differential revision: https://reviews.freebsd.org/D15173
This commit is contained in:
parent
e07db02261
commit
989b861f5c
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=332940
@ -54,15 +54,27 @@ static void
|
||||
__guard_setup(void)
|
||||
{
|
||||
static const int mib[2] = { CTL_KERN, KERN_ARND };
|
||||
volatile long tmp_stack_chk_guard[nitems(__stack_chk_guard)];
|
||||
size_t len;
|
||||
int error;
|
||||
int error, idx;
|
||||
|
||||
if (__stack_chk_guard[0] != 0)
|
||||
return;
|
||||
error = _elf_aux_info(AT_CANARY, __stack_chk_guard,
|
||||
sizeof(__stack_chk_guard));
|
||||
if (error == 0 && __stack_chk_guard[0] != 0)
|
||||
/*
|
||||
* Avoid using functions which might have stack protection
|
||||
* enabled, to update the __stack_chk_guard. First fetch the
|
||||
* data into a temporal array, then do manual volatile copy to
|
||||
* not allow optimizer to call memcpy() behind us.
|
||||
*/
|
||||
error = _elf_aux_info(AT_CANARY, (void *)tmp_stack_chk_guard,
|
||||
sizeof(tmp_stack_chk_guard));
|
||||
if (error == 0 && tmp_stack_chk_guard[0] != 0) {
|
||||
for (idx = 0; idx < nitems(__stack_chk_guard); idx++) {
|
||||
__stack_chk_guard[idx] = tmp_stack_chk_guard[idx];
|
||||
tmp_stack_chk_guard[idx] = 0;
|
||||
}
|
||||
return;
|
||||
}
|
||||
|
||||
len = sizeof(__stack_chk_guard);
|
||||
if (__sysctl(mib, nitems(mib), __stack_chk_guard, &len, NULL, 0) ==
|
||||
|
Loading…
Reference in New Issue
Block a user