Add an API for per-process disabling memory initialization.
Introduce an android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) API call
that may be used to disable zero- or pattern-init on non-MTE hardware,
or memory tagging on MTE hardware. The intent is that this function
may be called at any time, including when there are multiple threads
running.
Disabling zero- or pattern-init is quite trivial, we just need to set
a global variable to 0 via a Scudo API call (although there will be
some separate work required on the Scudo side to make this operation
thread-safe).
It is a bit more tricky to disable MTE across a process, because
the kernel does not provide an API for disabling tag checking in all
threads in a process, only per-thread. We need to send a signal to each
of the process's threads with a handler that issues the required prctl
call, and lock thread creation for the duration of the API call to
avoid races between thread enumeration and calls to pthread_create().
Bug: 135772972
Change-Id: I81ece86ace916eb6b435ab516cd431ec4b48a3bf
diff --git a/libc/bionic/malloc_common_dynamic.cpp b/libc/bionic/malloc_common_dynamic.cpp
index 6a82ae3..eeeaff9 100644
--- a/libc/bionic/malloc_common_dynamic.cpp
+++ b/libc/bionic/malloc_common_dynamic.cpp
@@ -70,6 +70,7 @@
#include "malloc_common_dynamic.h"
#include "malloc_heapprofd.h"
#include "malloc_limit.h"
+#include "memory_mitigation_state.h"
// =============================================================================
// Global variables instantations.
@@ -533,6 +534,9 @@
return MaybeInitGwpAsan(globals, *reinterpret_cast<bool*>(arg));
});
}
+ if (opcode == M_DISABLE_MEMORY_MITIGATIONS) {
+ return DisableMemoryMitigations(arg, arg_size);
+ }
// Try heapprofd's mallopt, as it handles options not covered here.
return HeapprofdMallopt(opcode, arg, arg_size);
}