Reland^2 "[MTE] remap stacks with PROT_MTE when requested by dlopened library"
Also enable stack MTE if main binary links in a library that needs it.
Otherwise the following is possible:
1. a binary doesn't require stack MTE, but links in libraries that use
stg on the stack
2. that binary later dlopens a library that requires stack MTE, and our
logic in dlopen remaps the stacks with MTE
3. the libraries from step 1 now have tagged pointers with missing tags
in memory, so things go wrong
This reverts commit f53e91cc810be2a36377f3b7765f50c89f1f0046.
Reason for revert: Fixed problem detected in b/324568991
Test: atest memtag_stack_dlopen_test with MTE enabled
Test: check crash is gone on fullmte build
Change-Id: I4a93f6814a19683c3ea5fe1e6d455df5459d31e1
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index 00faa5b..f091ff8 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -305,6 +305,14 @@
bool memtag_stack = false;
HeapTaggingLevel level =
__get_tagging_level(memtag_dynamic_entries, phdr_start, phdr_ct, load_bias, &memtag_stack);
+ // This is used by the linker (in linker.cpp) to communicate than any library linked by this
+ // executable enables memtag-stack.
+ if (__libc_shared_globals()->initial_memtag_stack) {
+ if (!memtag_stack) {
+ async_safe_format_log(ANDROID_LOG_INFO, "libc", "enabling PROT_MTE as requested by linker");
+ }
+ memtag_stack = true;
+ }
char* env = getenv("BIONIC_MEMTAG_UPGRADE_SECS");
static const char kAppProcessName[] = "app_process64";
const char* progname = __libc_shared_globals()->init_progname;
@@ -373,6 +381,8 @@
}
// We did not enable MTE, so we do not need to arm the upgrade timer.
__libc_shared_globals()->heap_tagging_upgrade_timer_sec = 0;
+ // We also didn't enable memtag_stack.
+ __libc_shared_globals()->initial_memtag_stack = false;
}
#else // __aarch64__
void __libc_init_mte(const memtag_dynamic_entries_t*, const void*, size_t, uintptr_t, void*) {}