zlib: properly clamp to uLong
On platforms where `unsigned long` and `size_t` differ in bit size, we want to clamp the buffers we pass to zlib to the former's size, as per d05d666977 (git-zlib: handle data streams larger than 4GB, 2026-05-08). The logic introduced in that commit performs a clamping to the bits, though, which fails to do what is needed here: If too many bytes are available in the buffers, we need to clamp to the maximum value of an `unsigned long`. Otherwise, we ask zlib to use too small buffers, in the worst case using 0 as the size (think: a value whose 32 lowest bits are all zero). Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Johannes Schindelin committed
Jun 18, 2026 at 13:50 UTC
ab3810eb6fffd95d39e9579945e360e8247eeda8
1 file changed
+9
-4
git-zlib.c
+9
-4
index b91cb323ae..d21adb3bf5 100644
--- a/git-zlib.c
+++ b/git-zlib.c
@@ -38,12 +38,17 @@ static inline uInt zlib_buf_cap(unsigned long len)
return (ZLIB_BUF_MAX < len) ? ZLIB_BUF_MAX : len;
}
+static inline uLong zlib_uLong_cap(size_t s)
+{
+ return s < ULONG_MAX_VALUE ? (uLong)s : ULONG_MAX_VALUE;
+}
+
static void zlib_pre_call(git_zstream *s)
{
s->z.next_in = s->next_in;
s->z.next_out = s->next_out;
- s->z.total_in = (uLong)(s->total_in & ULONG_MAX_VALUE);
- s->z.total_out = (uLong)(s->total_out & ULONG_MAX_VALUE);
+ s->z.total_in = zlib_uLong_cap(s->total_in);
+ s->z.total_out = zlib_uLong_cap(s->total_out);
s->z.avail_in = zlib_buf_cap(s->avail_in);
s->z.avail_out = zlib_buf_cap(s->avail_out);
}
@@ -60,7 +65,7 @@ static void zlib_post_call(git_zstream *s, int status)
* We track our own totals and verify only the low bits match.
*/
if ((s->z.total_out & ULONG_MAX_VALUE) !=
- ((s->total_out + bytes_produced) & ULONG_MAX_VALUE))
+ ((zlib_uLong_cap(s->total_out) + bytes_produced) & ULONG_MAX_VALUE))
BUG("total_out mismatch");
/*
* zlib does not update total_in when it returns Z_NEED_DICT,
@@ -68,7 +73,7 @@ static void zlib_post_call(git_zstream *s, int status)
*/
if (status != Z_NEED_DICT &&
(s->z.total_in & ULONG_MAX_VALUE) !=
- ((s->total_in + bytes_consumed) & ULONG_MAX_VALUE))
+ ((zlib_uLong_cap(s->total_in) + bytes_consumed) & ULONG_MAX_VALUE))
BUG("total_in mismatch");
s->total_out += bytes_produced;