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If vm_map_protect fails with KERN_RESOURCE_SHORTAGE, be sure to

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simplify modified entries before returning.

Reviewed by: alc, markj (earlier version), kib (earlier version)
Approved by: kib, markj (mentors, implicit)
Differential Revision: https://reviews.freebsd.org/D20753
This commit is contained in:
Doug Moore 2019-06-28 02:14:54 +00:00
parent a852cb9596
commit a72dce340d
1 changed files with 21 additions and 13 deletions
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34
sys/vm/vm_map.c
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@ -2454,6 +2454,7 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
vm_object_t obj;
struct ucred *cred;
vm_prot_t old_prot;
int rv;
if (start == end)
return (KERN_SUCCESS);
@ -2508,10 +2509,13 @@ again:
}
/*
* Do an accounting pass for private read-only mappings that
* now will do cow due to allowed write (e.g. debugger sets
* breakpoint on text segment)
* Before changing the protections, try to reserve swap space for any
* private (i.e., copy-on-write) mappings that are transitioning from
* read-only to read/write access. If a reservation fails, break out
* of this loop early and let the next loop simplify the entries, since
* some may now be mergeable.
*/
rv = KERN_SUCCESS;
vm_map_clip_start(map, entry, start);
for (current = entry; current->start < end; current = current->next) {
@ -2529,8 +2533,9 @@ again:
if (obj == NULL || (current->eflags & MAP_ENTRY_NEEDS_COPY)) {
if (!swap_reserve(current->end - current->start)) {
vm_map_unlock(map);
return (KERN_RESOURCE_SHORTAGE);
rv = KERN_RESOURCE_SHORTAGE;
end = current->end;
break;
}
crhold(cred);
current->cred = cred;
@ -2553,8 +2558,9 @@ again:
obj, current));
if (!swap_reserve(ptoa(obj->size))) {
VM_OBJECT_WUNLOCK(obj);
vm_map_unlock(map);
return (KERN_RESOURCE_SHORTAGE);
rv = KERN_RESOURCE_SHORTAGE;
end = current->end;
break;
}
crhold(cred);
@ -2564,11 +2570,14 @@ again:
}
/*
* Go back and fix up protections. [Note that clipping is not
* necessary the second time.]
* If enough swap space was available, go back and fix up protections.
* Otherwise, just simplify entries, since some may have been modified.
* [Note that clipping is not necessary the second time.]
*/
for (current = entry; current->start < end; current = current->next) {
if ((current->eflags & MAP_ENTRY_GUARD) != 0)
for (current = entry; current->start < end;
vm_map_simplify_entry(map, current), current = current->next) {
if (rv != KERN_SUCCESS ||
(current->eflags & MAP_ENTRY_GUARD) != 0)
continue;
old_prot = current->protection;
@ -2603,10 +2612,9 @@ again:
current->protection & MASK(current));
#undef MASK
}
vm_map_simplify_entry(map, current);
}
vm_map_unlock(map);
return (KERN_SUCCESS);
return (rv);
}
/*