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diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -4493,7 +4493,7 @@
vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
vm_size_t growsize, vm_prot_t prot, vm_prot_t max, int cow)
{
- vm_map_entry_t new_entry, prev_entry;
+ vm_map_entry_t new_entry, prev_entry, gap_entry;
vm_offset_t bot, gap_bot, gap_top, top;
vm_size_t init_ssize, sgp;
int orient, rv;
@@ -4575,11 +4575,14 @@
* read-ahead logic is never used for it. Re-use
* next_read of the gap entry to store
* stack_guard_page for vm_map_growstack().
+ * Similarly, since gap cannot have the backing object
+ * instantiated, store original stack protections into
+ * object offset.
*/
- if (orient == MAP_STACK_GROWS_DOWN)
- vm_map_entry_pred(new_entry)->next_read = sgp;
- else
- vm_map_entry_succ(new_entry)->next_read = sgp;
+ gap_entry = orient == MAP_STACK_GROWS_DOWN ?
+ vm_map_entry_pred(new_entry) : vm_map_entry_succ(new_entry);
+ gap_entry->next_read = sgp;
+ gap_entry->offset = prot;
} else {
(void)vm_map_delete(map, bot, top);
}
@@ -4599,6 +4602,7 @@
struct ucred *cred;
vm_offset_t gap_end, gap_start, grow_start;
vm_size_t grow_amount, guard, max_grow;
+ vm_prot_t prot;
rlim_t lmemlim, stacklim, vmemlim;
int rv, rv1 __diagused;
bool gap_deleted, grow_down, is_procstack;
@@ -4739,6 +4743,7 @@
}
if (grow_down) {
+ prot = gap_entry->offset;
grow_start = gap_entry->end - grow_amount;
if (gap_entry->start + grow_amount == gap_entry->end) {
gap_start = gap_entry->start;
@@ -4750,10 +4755,13 @@
vm_map_entry_resize(map, gap_entry, -grow_amount);
gap_deleted = false;
}
+
+ /*
+ * The gap_entry "offset" field is overloaded, see
+ * vm_map_stack_locked().
+ */
rv = vm_map_insert(map, NULL, 0, grow_start,
- grow_start + grow_amount,
- stack_entry->protection, stack_entry->max_protection,
- MAP_STACK_GROWS_DOWN);
+ grow_start + grow_amount, prot, prot, MAP_STACK_GROWS_DOWN);
if (rv != KERN_SUCCESS) {
if (gap_deleted) {
rv1 = vm_map_insert(map, NULL, 0, gap_start,

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