memory: fix refcount leak in memory_region_present
memory_region_present() leaks a reference to a MemoryRegion in the case "mr == container". While fixing it, avoid reference counting altogether for memory_region_present(), by using RCU only. The return value could in principle be already invalid immediately after memory_region_present returns, but presumably the caller knows that and it's using memory_region_present to probe for devices that are unpluggable, or something like that. The RCU critical section is needed anyway, because it protects as->current_map. Reported-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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24b41d66c8
commit
c6742b14fe
40
memory.c
40
memory.c
@ -1887,22 +1887,15 @@ static FlatRange *flatview_lookup(FlatView *view, AddrRange addr)
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sizeof(FlatRange), cmp_flatrange_addr);
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}
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bool memory_region_present(MemoryRegion *container, hwaddr addr)
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{
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MemoryRegion *mr = memory_region_find(container, addr, 1).mr;
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if (!mr || (mr == container)) {
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return false;
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}
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memory_region_unref(mr);
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return true;
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}
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bool memory_region_is_mapped(MemoryRegion *mr)
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{
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return mr->container ? true : false;
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}
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MemoryRegionSection memory_region_find(MemoryRegion *mr,
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/* Same as memory_region_find, but it does not add a reference to the
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* returned region. It must be called from an RCU critical section.
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*/
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static MemoryRegionSection memory_region_find_rcu(MemoryRegion *mr,
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hwaddr addr, uint64_t size)
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{
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MemoryRegionSection ret = { .mr = NULL };
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@ -1924,11 +1917,10 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
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}
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range = addrrange_make(int128_make64(addr), int128_make64(size));
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rcu_read_lock();
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view = atomic_rcu_read(&as->current_map);
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fr = flatview_lookup(view, range);
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if (!fr) {
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goto out;
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return ret;
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}
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while (fr > view->ranges && addrrange_intersects(fr[-1].addr, range)) {
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@ -1944,12 +1936,32 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
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ret.size = range.size;
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ret.offset_within_address_space = int128_get64(range.start);
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ret.readonly = fr->readonly;
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return ret;
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}
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MemoryRegionSection memory_region_find(MemoryRegion *mr,
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hwaddr addr, uint64_t size)
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{
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MemoryRegionSection ret;
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rcu_read_lock();
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ret = memory_region_find_rcu(mr, addr, size);
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if (ret.mr) {
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memory_region_ref(ret.mr);
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out:
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}
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rcu_read_unlock();
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return ret;
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}
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bool memory_region_present(MemoryRegion *container, hwaddr addr)
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{
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MemoryRegion *mr;
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rcu_read_lock();
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mr = memory_region_find_rcu(container, addr, 1).mr;
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rcu_read_unlock();
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return mr && mr != container;
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}
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void address_space_sync_dirty_bitmap(AddressSpace *as)
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{
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FlatView *view;
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