procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
/*
* mpatch.cc - fuzzer harness for mpatch.c
*
* Copyright 2018, Google Inc.
*
* This software may be used and distributed according to the terms of
* the GNU General Public License, incorporated herein by reference.
*/
#include <iostream>
#include <memory>
#include <stdint.h>
#include <stdlib.h>
#include <vector>
#include "fuzzutil.h"
extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
{
return 0;
}
// To avoid having too many OOMs from the fuzzer infrastructure, we'll
// skip patch application if the resulting fulltext would be bigger
// than 10MiB.
#define MAX_OUTPUT_SIZE 10485760
extern "C" {
#include "bitmanipulation.h"
#include "mpatch.h"
struct mpatchbin {
std::unique_ptr<char[]> data;
size_t len;
};
static mpatch_flist *getitem(void *vbins, ssize_t pos)
{
std::vector<mpatchbin> *bins = (std::vector<mpatchbin> *)vbins;
const mpatchbin &bin = bins->at(pos + 1);
struct mpatch_flist *res;
LOG(2) << "mpatch_decode " << bin.len << std::endl;
if (mpatch_decode(bin.data.get(), bin.len, &res) < 0)
return NULL;
return res;
}
// input format:
// u8 number of inputs
// one u16 for each input, its length
// the inputs
int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
if (!Size) {
return 0;
}
// First byte of data is how many texts we expect, first text
// being the base the rest being the deltas.
ssize_t numtexts = Data[0];
if (numtexts < 2) {
// No point if we don't have at least a base text and a delta...
return 0;
}
// Each text will be described by a byte for how long it
// should be, so give up if we don't have enough.
if ((Size - 1) < (numtexts * 2)) {
return 0;
}
size_t consumed = 1 + (numtexts * 2);
LOG(2) << "input contains " << Size << std::endl;
LOG(2) << numtexts << " texts, consuming " << consumed << std::endl;
std::vector<mpatchbin> bins;
bins.reserve(numtexts);
for (int i = 0; i < numtexts; ++i) {
mpatchbin bin;
size_t nthsize = getbeuint16((char *)Data + 1 + (2 * i));
LOG(2) << "text " << i << " is " << nthsize << std::endl;
char *start = (char *)Data + consumed;
consumed += nthsize;
if (consumed > Size) {
LOG(2) << "ran out of data, consumed " << consumed
<< " of " << Size << std::endl;
return 0;
}
bin.len = nthsize;
bin.data.reset(new char[nthsize]);
memcpy(bin.data.get(), start, nthsize);
bins.push_back(std::move(bin));
}
LOG(2) << "mpatch_flist" << std::endl;
struct mpatch_flist *patch =
mpatch_fold(&bins, getitem, 0, numtexts - 1);
if (!patch) {
return 0;
}
LOG(2) << "mpatch_calcsize" << std::endl;
ssize_t outlen = mpatch_calcsize(bins[0].len, patch);
LOG(2) << "outlen " << outlen << std::endl;
if (outlen < 0 || outlen > MAX_OUTPUT_SIZE) {
goto cleanup;
}
{
char *dest = (char *)malloc(outlen);
LOG(2) << "expecting " << outlen << " total bytes at "
<< (void *)dest << std::endl;
mpatch_apply(dest, bins[0].data.get(), bins[0].len, patch);
free(dest);
LOG(1) << "applied a complete patch" << std::endl;
}
cleanup:
mpatch_lfree(patch);
return 0;
}
} // extern "C"