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pretty: fix integer overflow in wrapping format

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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>
This commit is contained in:
Patrick Steinhardt 2022-12-01 15:46:49 +01:00 committed by Junio C Hamano
parent 1de69c0cdd
commit 48050c42c7
3 changed files with 23 additions and 1 deletions
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8
git-compat-util.h
View File

@ -918,6 +918,14 @@ static inline size_t st_sub(size_t a, size_t b)
return a - b;
}
static inline int cast_size_t_to_int(size_t a)
{
if (a > INT_MAX)
die("number too large to represent as int on this platform: %"PRIuMAX,
(uintmax_t)a);
return (int)a;
}
#ifdef HAVE_ALLOCA_H
# include <alloca.h>
# define xalloca(size) (alloca(size))

4
pretty.c
View File

@ -915,7 +915,9 @@ static void strbuf_wrap(struct strbuf *sb, size_t pos,
if (pos)
strbuf_add(&tmp, sb->buf, pos);
strbuf_add_wrapped_text(&tmp, sb->buf + pos,
(int) indent1, (int) indent2, (int) width);
cast_size_t_to_int(indent1),
cast_size_t_to_int(indent2),
cast_size_t_to_int(width));
strbuf_swap(&tmp, sb);
strbuf_release(&tmp);
}

12
t/t4205-log-pretty-formats.sh
View File

@ -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.