Merge "Allow the kernel to upgrade ASYNC mode processes to SYNC mode."
diff --git a/libc/bionic/heap_tagging.cpp b/libc/bionic/heap_tagging.cpp
index ffbabb9..41aa205 100644
--- a/libc/bionic/heap_tagging.cpp
+++ b/libc/bionic/heap_tagging.cpp
@@ -139,7 +139,12 @@
}
if (tag_level == M_HEAP_TAGGING_LEVEL_ASYNC) {
- set_tcf_on_all_threads(PR_MTE_TCF_ASYNC);
+ // When entering ASYNC mode, specify that we want to allow upgrading to SYNC by OR'ing in
+ // the SYNC flag. But if the kernel doesn't support specifying multiple TCF modes, fall back
+ // to specifying a single mode.
+ if (!set_tcf_on_all_threads(PR_MTE_TCF_ASYNC | PR_MTE_TCF_SYNC)) {
+ set_tcf_on_all_threads(PR_MTE_TCF_ASYNC);
+ }
#if defined(USE_SCUDO)
scudo_malloc_set_track_allocation_stacks(0);
#endif
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index 069ebb0..3a8513f 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -311,7 +311,11 @@
unsigned long prctl_arg = PR_TAGGED_ADDR_ENABLE | PR_MTE_TAG_SET_NONZERO;
prctl_arg |= (level == M_HEAP_TAGGING_LEVEL_SYNC) ? PR_MTE_TCF_SYNC : PR_MTE_TCF_ASYNC;
- if (prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg, 0, 0, 0) == 0) {
+ // When entering ASYNC mode, specify that we want to allow upgrading to SYNC by OR'ing in the
+ // SYNC flag. But if the kernel doesn't support specifying multiple TCF modes, fall back to
+ // specifying a single mode.
+ if (prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg | PR_MTE_TCF_SYNC, 0, 0, 0) == 0 ||
+ prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg, 0, 0, 0) == 0) {
__libc_shared_globals()->initial_heap_tagging_level = level;
return;
}