Assigning strlen() to a uint32_t and then asserting that it isn't too large doesn't catch the case of an input string 4G in length. Thankfully, the incoming string can never be that large: if the export name is reflecting what the client asked about, we already guarantee that we drop the NBD connection if the client tries to send more than 32M in a single NBD_OPT_* request; and if the export name is coming from qemu, nbd_receive_negotiate() asserted that strlen(info->name) <= NBD_MAX_STRING_SIZE. Still, it doesn't hurt to be more explicit in how we write our assertion that we are aware that no wraparound is possible.
Fixes: 93676c88 ("nbd: Don't send oversize strings", v4.2.0) Reported-by: Dr. David Alan Gilbert <dgilb...@redhat.com> Signed-off-by: Eric Blake <ebl...@redhat.com> --- nbd/client.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/nbd/client.c b/nbd/client.c index 60c9f4941a..b601ee97e5 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -658,7 +658,7 @@ static int nbd_send_meta_query(QIOChannel *ioc, uint32_t opt, char *p; data_len = sizeof(export_len) + export_len + sizeof(queries); - assert(export_len <= NBD_MAX_STRING_SIZE); + assert(strlen(export) <= NBD_MAX_STRING_SIZE); if (query) { query_len = strlen(query); data_len += sizeof(query_len) + query_len; -- 2.37.3