When we're writing out a new objects/info/packs file, we read back the
old one to try to keep the ordering the same. When we see a line
starting with "P", we expect "P pack-1234..." and blindly jump to "line
+ 2" to parse the pack name. If we saw a line with _just_ "P" and
nothing else, we'd jump past the end of the buffer and start reading
arbitrary memory.
This shouldn't be a big attack vector, as the files are local to the
repository and written by us, but it's clearly worth fixing (we do read
remote copies of the file for dumb-http fetches, but using a totally
different parser!).
Let's instead use skip_prefix() here, which avoids pointer arithmetic
altogether. Note that this converts our switch statement to an if/else
chain, making it slightly more verbose. But it will also make it easier
to do a few follow-on cleanups.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
server-info.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/server-info.c b/server-info.c
index e2b2d6a27a..b61a6be4c2 100644
--- a/server-info.c
+++ b/server-info.c
@@ -112,9 +112,9 @@ static struct pack_info *find_pack_by_name(const char *name)
/* Returns non-zero when we detect that the info in the
* old file is useless.
*/
-static int parse_pack_def(const char *line, int old_cnt)
+static int parse_pack_def(const char *packname, int old_cnt)
{
- struct pack_info *i = find_pack_by_name(line + 2);
+ struct pack_info *i = find_pack_by_name(packname);
if (i) {
i->old_num = old_cnt;
return 0;
@@ -139,24 +139,26 @@ static int read_pack_info_file(const char *infofile)
return 1; /* nonexistent is not an error. */
while (fgets(line, sizeof(line), fp)) {
+ const char *arg;
int len = strlen(line);
if (len && line[len-1] == '\n')
line[--len] = 0;
if (!len)
continue;
- switch (line[0]) {
- case 'P': /* P name */
- if (parse_pack_def(line, old_cnt++))
+ if (skip_prefix(line, "P ", &arg)) {
+ /* P name */
+ if (parse_pack_def(arg, old_cnt++))
goto out_stale;
- break;
- case 'D': /* we used to emit D but that was misguided. */
- case 'T': /* we used to emit T but nobody uses it. */
+ } else if (line[0] == 'D') {
+ /* we used to emit D but that was misguided. */
goto out_stale;
- default:
+ } else if (line[0] == 'T') {
+ /* we used to emit T but nobody uses it. */
+ goto out_stale;
+ } else {
error("unrecognized: %s", line);
- break;
}
}
fclose(fp);
--
2.21.0.714.gd1be1d035b
