[PATCH 1/5] test-delta: read input into a heap buffer
- From
Jeff King <peff@peff.net>
- Date
- Aug 30, 2018, 07:07 UTC
- Message-ID
- <20180830070751.GA15420@sigill.intra.peff.net>
- In-Reply-To
- <20180830070548.GA15081@sigill.intra.peff.net>
We currently read the input to test-delta by mmap()-ing it. However, memory-checking tools like valgrind and ASan are less able to detect reads/writes past the end of an mmap'd buffer, because the OS is likely to give us extra bytes to pad out the final page size. So instead, let's read into a heap buffer.
As a bonus, this also makes it possible to write tests with empty bases, as mmap() will complain about a zero-length map.
This is based on a patch by Jann Horn <jannh@google.com> which actually aligned the data at the end of a page, and followed it with another page marked with mprotect(). That would detect problems even without a tool like ASan, but it was significantly more complex and may have introduced portability problems. By comparison, this approach pushes the complexity onto existing memory-checking tools.
Note that this could be done even more simply by using strbuf_read_file(), but that would defeat the purpose: strbufs generally overallocate (and at the very least include a trailing NUL which we do not care about), which would defeat most memory checkers.
Signed-off-by: Jeff King <peff@peff.net> --- t/helper/test-delta.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/t/helper/test-delta.c b/t/helper/test-delta.c index 34c7259248..e749a49c88 100644 --- a/t/helper/test-delta.c +++ b/t/helper/test-delta.c @@ -34,8 +34,8 @@ int cmd__delta(int argc, const char **argv) return 1; } from_size = st.st_size; - from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0); - if (from_buf == MAP_FAILED) { + from_buf = xmalloc(from_size); + if (read_in_full(fd, from_buf, from_size) < 0) { perror(argv[2]); close(fd); return 1; @@ -48,8 +48,8 @@ int cmd__delta(int argc, const char **argv) return 1; } data_size = st.st_size; - data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0); - if (data_buf == MAP_FAILED) { + data_buf = xmalloc(data_size); + if (read_in_full(fd, data_buf, data_size) < 0) { perror(argv[3]); close(fd); return 1;
-- 2.19.0.rc1.539.g3876d0831e