"Jeff Hostetler via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes: > From: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx> > > Use FLEX_ALLOC_STR() to allocate the `struct untracked_cache_dir` > for the root directory. Get rid of unsafe code that might fail to > initialize the `name` field (if FLEX_ARRAY is not 1). This will > make it clear that we intend to have a structure with an empty > string following it. > > A problem was observed on Windows where the length of the memset() was > too short, so the first byte of the name field was not zeroed. This > resulted in the name field having garbage from a previous use of that > area of memory. > > The record for the root directory was then written to the untracked-cache > extension in the index. This garbage would then be visible to future > commands when they reloaded the untracked-cache extension. > > Since the directory record for the root directory had garbage in the > `name` field, the `t/helper/test-tool dump-untracked-cache` tool > printed this garbage as the path prefix (rather than '/') for each > directory in the untracked cache as it recursed. > > Signed-off-by: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx> > --- > dir: fix malloc of root untracked_cache_dir Nicely spotted. The problematic code was introduced in 2015, a year before these FLEX_ALLOC_*() helpers were introduced. The result is of course correct and much easier to read, as the necessary "ask for a region of calloc'ed memory with an additional byte for terminating NUL beyond strlen()" is hidden in the helper. Will queue; thanks. > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-884%2Fjeffhostetler%2Funtracked-cache-corruption-v1 > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-884/jeffhostetler/untracked-cache-corruption-v1 > Pull-Request: https://github.com/gitgitgadget/git/pull/884 > > dir.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/dir.c b/dir.c > index d153a63bbd14..fd8aa7c40faa 100644 > --- a/dir.c > +++ b/dir.c > @@ -2730,11 +2730,8 @@ static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *d > return NULL; > } > > - if (!dir->untracked->root) { > - const int len = sizeof(*dir->untracked->root); > - dir->untracked->root = xmalloc(len); > - memset(dir->untracked->root, 0, len); > - } > + if (!dir->untracked->root) > + FLEX_ALLOC_STR(dir->untracked->root, name, ""); > > /* Validate $GIT_DIR/info/exclude and core.excludesfile */ > root = dir->untracked->root; > > base-commit: 966e671106b2fd38301e7c344c754fd118d0bb07
