| From c1b7eef9fa4aaefbf7d0507505c3bb2914e1ad6b Mon Sep 17 00:00:00 2001 |
| From: Daniel Axtens <dja@axtens.net> |
| Date: Thu, 16 Sep 2021 01:29:54 +1000 |
| Subject: [PATCH 26/38] net/dns: Fix double-free addresses on corrupt DNS |
| response |
| |
| grub_net_dns_lookup() takes as inputs a pointer to an array of addresses |
| ("addresses") for the given name, and pointer to a number of addresses |
| ("naddresses"). grub_net_dns_lookup() is responsible for allocating |
| "addresses", and the caller is responsible for freeing it if |
| "naddresses" > 0. |
| |
| The DNS recv_hook will sometimes set and free the addresses array, |
| for example if the packet is too short: |
| |
| if (ptr + 10 >= nb->tail) |
| { |
| if (!*data->naddresses) |
| grub_free (*data->addresses); |
| grub_netbuff_free (nb); |
| return GRUB_ERR_NONE; |
| } |
| |
| Later on the nslookup command code unconditionally frees the "addresses" |
| array. Normally this is fine: the array is either populated with valid |
| data or is NULL. But in these sorts of error cases it is neither NULL |
| nor valid and we get a double-free. |
| |
| Only free "addresses" if "naddresses" > 0. |
| |
| It looks like the other use of grub_net_dns_lookup() is not affected. |
| |
| Signed-off-by: Daniel Axtens <dja@axtens.net> |
| Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> |
| --- |
| grub-core/net/dns.c | 6 ++++-- |
| 1 file changed, 4 insertions(+), 2 deletions(-) |
| |
| diff --git a/grub-core/net/dns.c b/grub-core/net/dns.c |
| index 27c5f4142..841ede51e 100644 |
| --- a/grub-core/net/dns.c |
| +++ b/grub-core/net/dns.c |
| @@ -667,9 +667,11 @@ grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)), |
| grub_net_addr_to_str (&addresses[i], buf); |
| grub_printf ("%s\n", buf); |
| } |
| - grub_free (addresses); |
| if (naddresses) |
| - return GRUB_ERR_NONE; |
| + { |
| + grub_free (addresses); |
| + return GRUB_ERR_NONE; |
| + } |
| return grub_error (GRUB_ERR_NET_NO_DOMAIN, N_("no DNS record found")); |
| } |
| |
| -- |
| 2.37.0.rc0.104.g0611611a94-goog |
| |