attr: fix overflow when upserting attribute with overly long name

The function `git_attr_internal()` is called to upsert attributes into
the global map. And while all callers pass a `size_t`, the function
itself accepts an `int` as the attribute name's length. This can lead to
an integer overflow in case the attribute name is longer than `INT_MAX`.

Now this overflow seems harmless as the first thing we do is to call
`attr_name_valid()`, and that function only succeeds in case all chars
in the range of `namelen` match a certain small set of chars. We thus
can't do an out-of-bounds read as NUL is not part of that set and all
strings passed to this function are NUL-terminated. And furthermore, we
wouldn't ever read past the current attribute name anyway due to the
same reason. And if validation fails we will return early.

On the other hand it feels fragile to rely on this behaviour, even more
so given that we pass `namelen` to `FLEX_ALLOC_MEM()`. So let's instead
just do the correct thing here and accept a `size_t` as line length.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/attr.c b/attr.c
index 4ef85d668b54960d692b6bae127920c10045c4ca..39ce0eb95e985e062e1a2dae65dac0b8d68178fc 100644 (file)
--- a/attr.c
+++ b/attr.c
@@ -210,7 +210,7 @@ static void report_invalid_attr(const char *name, size_t len,
  * dictionary.  If no entry is found, create a new attribute and store it in
  * the dictionary.
  */
-static const struct git_attr *git_attr_internal(const char *name, int namelen)
+static const struct git_attr *git_attr_internal(const char *name, size_t namelen)
 {
        struct git_attr *a;