| Message ID | 20200508063954.256593-1-irogers@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | libbpf hashmap: fix undefined behavior in hash_bits | expand |
diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h index d5ef212a55ba..781db653d16c 100644 --- a/tools/lib/bpf/hashmap.h +++ b/tools/lib/bpf/hashmap.h @@ -19,6 +19,8 @@ static inline size_t hash_bits(size_t h, int bits) { /* shuffle bits and return requested number of upper bits */ + if (bits == 0) + return 0; return (h * 11400714819323198485llu) >> (__WORDSIZE - bits); }
If bits is 0, the case when the map is empty, then the >> is the size of the register which is undefined behavior - on x86 it is the same as a shift by 0. Fix by handling the 0 case explicitly. Signed-off-by: Ian Rogers <irogers@google.com> --- tools/lib/bpf/hashmap.h | 2 ++ 1 file changed, 2 insertions(+)