pretty: fix integer overflow in wrapping format

The `%w(width,indent1,indent2)` formatting directive can be used to
rewrap text to a specific width and is designed after git-shortlog(1)'s
`-w` parameter. While the three parameters are all stored as `size_t`
internally, `strbuf_add_wrapped_text()` accepts integers as input. As a
result, the casted integers may overflow. As these now-negative integers
are later on passed to `strbuf_addchars()`, we will ultimately run into
implementation-defined behaviour due to casting a negative number back
to `size_t` again. On my platform, this results in trying to allocate
9000 petabyte of memory.

Fix this overflow by using `cast_size_t_to_int()` so that we reject
inputs that cannot be represented as an integer.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 1d768f7244..c88b64d08b 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -887,6 +887,18 @@ test_expect_success 'log --pretty with magical wrapping directives' '
 	test_cmp expect actual
 '
 
+test_expect_success SIZE_T_IS_64BIT 'log --pretty with overflowing wrapping directive' '
+	cat >expect <<-EOF &&
+	fatal: number too large to represent as int on this platform: 2147483649
+	EOF
+	test_must_fail git log -1 --pretty="format:%w(2147483649,1,1)%d" 2>error &&
+	test_cmp expect error &&
+	test_must_fail git log -1 --pretty="format:%w(1,2147483649,1)%d" 2>error &&
+	test_cmp expect error &&
+	test_must_fail git log -1 --pretty="format:%w(1,1,2147483649)%d" 2>error &&
+	test_cmp expect error
+'
+
 test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' '
 	# We only assert that this command does not crash. This needs to be
 	# executed with the address sanitizer to demonstrate failure.