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libfuzzer: fix looking at wrong memory for pc counters

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this fix bypasses the slice bounds, reading garbage data for up to the
last 7 bits (which are technically supposed to be ignored). that's going
to need to be fixed, let's fix that along with switching from byte elems
to usize elems.
This commit is contained in:
Andrew Kelley 2024-08-05 18:37:19 -07:00
parent 5f5a7b53a4
commit 529df8c007
1 changed files with 10 additions and 10 deletions
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20
lib/fuzzer.zig
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@ -276,7 +276,7 @@ const Fuzzer = struct {
.score = 0,
}, {});
} else {
if (f.n_runs % 1000 == 0) f.dumpStats();
if (f.n_runs % 10000 == 0) f.dumpStats();
const analysis = f.analyzeLastRun();
const gop = f.recent_cases.getOrPutAssumeCapacity(.{
@ -303,16 +303,16 @@ const Fuzzer = struct {
{
const seen_pcs = f.seen_pcs.items[@sizeOf(SeenPcsHeader) + f.flagged_pcs.len * @sizeOf(usize) ..];
for (seen_pcs, 0..) |*elem, i| {
const byte_i = i / 8;
const byte_i = i * 8;
const mask: u8 =
(@as(u8, @intFromBool(f.pc_counters[byte_i + 0] != 0)) << 0) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 1] != 0)) << 1) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 2] != 0)) << 2) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 3] != 0)) << 3) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 4] != 0)) << 4) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 5] != 0)) << 5) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 6] != 0)) << 6) |
(@as(u8, @intFromBool(f.pc_counters[byte_i + 7] != 0)) << 7);
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 0] != 0)) << 0) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 1] != 0)) << 1) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 2] != 0)) << 2) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 3] != 0)) << 3) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 4] != 0)) << 4) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 5] != 0)) << 5) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 6] != 0)) << 6) |
(@as(u8, @intFromBool(f.pc_counters.ptr[byte_i + 7] != 0)) << 7);
_ = @atomicRmw(u8, elem, .Or, mask, .monotonic);
}