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authorBoshan Sun <[email protected]>2017-11-20 10:21:29 -0800
committerBoshan Sun <[email protected]>2017-11-20 10:21:29 -0800
commit23e511d470e6795799c29b5ccb2ab6a17589e543 (patch)
treeebf6266e2e0b87c58d6b36c5cc6e24da5fe9cf1c /erts/emulator
parent4c736d27d32b5334d8ba978c100a591caf0ac604 (diff)
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Fix integer overflow when set a large maximum value for atom table
When setting maximum atom table size using +t option, there will be a integer overflow for a large size. $ erl +t2147482625 ll_alloc: Cannot allocate 18446744073692774400 bytes of memory (of type "atom_tab"). The overflow is caused by the arithmetic operations on int type. When 2147482625 + 1024 it will become -2147483647 due to the signed integerger overflow. Then the result will be resized to Uint type, which is a unsigned long type, the negative int will first be expand to 64 bits long via sign extension, then change to unsigned type, which becomes 18446744073692774400. The fix is done by convert `limit` to Uint type before doing any arithmetic operation. This will expand variable to 64 bits long type via zero extension, then the following operation are all positive, therefore no overflow will happen. Note: here we assume the int `limit` passed in is always positive. If some future change cause the `limit` passed in maybe negative, then the current fix will also cause overflow.
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/index.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/erts/emulator/beam/index.c b/erts/emulator/beam/index.c
index a1f6f54543..7bf1a032c1 100644
--- a/erts/emulator/beam/index.c
+++ b/erts/emulator/beam/index.c
@@ -58,7 +58,7 @@ IndexTable*
erts_index_init(ErtsAlcType_t type, IndexTable* t, char* name,
int size, int limit, HashFunctions fun)
{
- Uint base_size = ((limit+INDEX_PAGE_SIZE-1)/INDEX_PAGE_SIZE)*sizeof(IndexSlot*);
+ Uint base_size = (((Uint)limit+INDEX_PAGE_SIZE-1)/INDEX_PAGE_SIZE)*sizeof(IndexSlot*);
hash_init(type, &t->htable, name, 3*size/4, fun);
t->size = 0;