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Commit 0cc30e0e (strbuf_getwholeline: use getdelim if it is available, 2015-04-16) tries to clean up after getdelim() returns EOF, but gets one case wrong, which can lead in some obscure cases to us reading uninitialized memory. After getdelim() returns -1, we re-initialize the strbuf only if sb->buf is NULL. The thinking was that either: 1. We fed an existing allocated buffer to getdelim(), and at most it would have realloc'd, leaving our NUL in place. 2. We didn't have a buffer to feed, so we gave getdelim() NULL; sb->buf will remain NULL, and we just want to restore the empty slopbuf. But that second case isn't quite right. getdelim() may allocate a buffer, write nothing into it, and then return EOF. The resulting strbuf rightfully has sb->len set to "0", but is missing the NUL terminator in the first byte. Most call-sites are fine with this. They see the EOF and don't bother looking at the strbuf. Or they notice that sb->len is empty, and don't look at the contents. But there's at least one case that does neither, and relies on parsing the resulting (possibly zero-length) string: fast-import. You can see this in action with the new test (though we probably only notice failure there when run with --valgrind or ASAN). We can fix this by unconditionally resetting the strbuf when we have a buffer after getdelim(). That fixes case 2 above. Case 1 is probably already fine in practice, but it does not hurt for us to re-assert our invariants (especially because we are relying on whatever getdelim() happens to do, which may vary from platform to platform). Our fix covers that case, too. Signed-off-by:
Jeff King <peff@peff.net> Signed-off-by:
Junio C Hamano <gitster@pobox.com>
b7090430
