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Fix SEGV in Dbus code.

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A 'AddDhcpLease' DBus message which fails to allocate
a DHCP lease will cause dnsmasq to dereference a NULL pointer
and crash.

Allocation failure can happen if the particular
flavour (IPv4 pr IPv6) of DHCP is not configured in
this dnsmasq instance, or if the configured limit on
DHCP leases is reached or (unlikley) if dnsmasq cannot
allocate memory.

This patch provides error returns for all these situations.

This patch is inspired by a patch from
Stefan Hanreich <s.hanreich@proxmox.com> which was prompted by
a bug report from Lou Lécrivain.
This commit is contained in:
Simon Kelley
2025-11-28 16:10:37 +00:00
parent 57a2f5778c
commit eb60168382
1 changed files with 16 additions and 3 deletions
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15
src/dbus.c
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@@ -530,8 +530,8 @@ static DBusMessage *dbus_add_lease(DBusMessage* message)
union all_addr addr;
time_t now = dnsmasq_time();
unsigned char dhcp_chaddr[DHCP_CHADDR_MAX];
DBusMessageIter iter, array_iter;
if (!dbus_message_iter_init(message, &iter))
return dbus_message_new_error(message, DBUS_ERROR_INVALID_ARGS,
"Failed to initialize dbus message iter");
@@ -599,6 +599,10 @@ static DBusMessage *dbus_add_lease(DBusMessage* message)
if (inet_pton(AF_INET, ipaddr, &addr.addr4))
{
if (!daemon->dhcp)
return dbus_message_new_error(message, DBUS_ERROR_INVALID_ARGS,
"DHCPv4 not configured");
if (ia_id != 0 || is_temporary)
return dbus_message_new_error(message, DBUS_ERROR_INVALID_ARGS,
"ia_id and is_temporary must be zero for IPv4 lease");
@@ -609,9 +613,14 @@ static DBusMessage *dbus_add_lease(DBusMessage* message)
#ifdef HAVE_DHCP6
else if (inet_pton(AF_INET6, ipaddr, &addr.addr6))
{
if (!daemon->doing_dhcp6)
return dbus_message_new_error(message, DBUS_ERROR_INVALID_ARGS,
"DHCPv6 not configured");
if (!(lease = lease6_find_by_addr(&addr.addr6, 128, 0)))
lease = lease6_allocate(&addr.addr6,
is_temporary ? LEASE_TA : LEASE_NA);
if (lease)
lease_set_iaid(lease, ia_id);
}
#endif
@@ -619,6 +628,10 @@ static DBusMessage *dbus_add_lease(DBusMessage* message)
return dbus_message_new_error_printf(message, DBUS_ERROR_INVALID_ARGS,
"Invalid IP address '%s'", ipaddr);
if (!lease)
return dbus_message_new_error_printf(message, DBUS_ERROR_INVALID_ARGS,
"unable to allocate lease for IP address '%s'", ipaddr);
hw_len = parse_hex((char*)hwaddr, dhcp_chaddr, DHCP_CHADDR_MAX, NULL, &hw_type);
if (hw_len < 0)
return dbus_message_new_error_printf(message, DBUS_ERROR_INVALID_ARGS,