From: Daniel Axtens <d...@axtens.net> 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 <d...@axtens.net> Reviewed-by: Daniel Kiper <daniel.ki...@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")); } -- 2.11.0 _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel