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show-branch: store resolved head in heap buffer

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We resolve HEAD and copy the result to a fixed-size buffer
with memcpy, never checking that it actually fits. This bug
dates back to 8098a178b (Add git-symbolic-ref, 2005-09-30).
Before that we used readlink(), which took a maximum buffer
size.

We can fix this by using resolve_refdup(), which duplicates
the buffer on the heap. That also lets us just check
for a NULL pointer to see if we have resolved HEAD, and
drop the extra head_p variable.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2017-02-14 12:27:45 -05:00 committed by Junio C Hamano
parent e6a7c75298
commit d9e557a320
1 changed files with 5 additions and 14 deletions
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19
builtin/show-branch.c
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@ -473,8 +473,7 @@ static void snarf_refs(int head, int remotes)
static int rev_is_head(char *head, char *name,
unsigned char *head_sha1, unsigned char *sha1)
{
if ((!head[0]) ||
(head_sha1 && sha1 && hashcmp(head_sha1, sha1)))
if (!head || (head_sha1 && sha1 && hashcmp(head_sha1, sha1)))
return 0;
if (starts_with(head, "refs/heads/"))
head += 11;
@ -621,8 +620,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
int all_heads = 0, all_remotes = 0;
int all_mask, all_revs;
enum rev_sort_order sort_order = REV_SORT_IN_GRAPH_ORDER;
char head[128];
const char *head_p;
char *head;
struct object_id head_oid;
int merge_base = 0;
int independent = 0;
@ -786,17 +784,10 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
snarf_refs(all_heads, all_remotes);
}
head_p = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
head_oid.hash, NULL);
if (head_p) {
size_t head_len = strlen(head_p);
memcpy(head, head_p, head_len + 1);
}
else {
head[0] = 0;
}
head = resolve_refdup("HEAD", RESOLVE_REF_READING,
head_oid.hash, NULL);
if (with_current_branch && head_p) {
if (with_current_branch && head) {
int has_head = 0;
for (i = 0; !has_head && i < ref_name_cnt; i++) {
/* We are only interested in adding the branch