stream_libarchive: fix hangs when demuxer does out of bound seeks

This happened with a .flac file inside an archive. It tried to seek
beyond the end of the archive entry in a format where seeking isn't
supported. stream_libarchive handles these situations by skipping data.
But when the end of the archive is reached, archive_read_data() returns
0. While libarchive didn't bother to fucking document this, they do say
it's supposed to work like read(), so I guess a return value of 0 really
means EOF. So change the "< 0" to "<= 0". Also add some error logging.

The same file actually worked without out of bounds reads when
extracted, so there still might be something very wrong.

(cherry picked from commit 7e85dc2167b7524308159915d5c1d3341464977f)

1 files changed, 9 insertions, 2 deletions

diff --git a/stream/stream_libarchive.c b/stream/stream_libarchive.c
index bb25c6ad84..119af8eea4 100644
--- a/stream/stream_libarchive.c
+++ b/stream/stream_libarchive.c
@@ -432,8 +432,15 @@ static int archive_entry_seek(stream_t *s, int64_t newpos)
             int size = MPMIN(newpos - s->pos, sizeof(buffer));
             locale_t oldlocale = uselocale(p->mpa->locale);
             int r = archive_read_data(p->mpa->arch, buffer, size);
-            if (r < 0) {
-                MP_ERR(s, "%s\n", archive_error_string(p->mpa->arch));
+            if (r <= 0) {
+                if (r == 0 && newpos > p->entry_size) {
+                    MP_ERR(s, "demuxer trying to seek beyond end of archive "
+                           "entry\n");
+                } else if (r == 0) {
+                    MP_ERR(s, "end of archive entry reached while seeking\n");
+                } else {
+                    MP_ERR(s, "%s\n", archive_error_string(p->mpa->arch));
+                }
                 uselocale(oldlocale);
                 if (mp_archive_check_fatal(p->mpa, r)) {
                     mp_archive_free(p->mpa);