[PATCH (pushed)] udevListInterfaces: Honour array length for zero-length NULL arrays (CVE-2024-8235)

The refactor of 'udevListInterfacesByStatus()' which attempted to make it usable as backend for 'udevNumOfInterfacesByStatus()' neglected to consider the corner case of 'g_new0(..., 0)' returning NULL if the user actually requests 0 elements. As the code was modified to report the full number of interfaces in the system when the list of names is NULL, the RPC code would be asked to serialize a NULL-list of interface names with declared lenth of 1+ causing a crash. To fix this corner case we make callers pass '-1' as @names_len (it's conveniently an 'int' due to RPC type usage) if they don't wish to fetch the actual list and convert all decisions to be done on @names_len being non-negative instead of @names being non-NULL. CVE-2024-8235 Fixes: bc596f275129bc11b2c4bcf737d380c9e8aeb72d Resolves: https://issues.redhat.com/browse/RHEL-55373 Reported-by: Yanqiu Zhang <yanqzhan(a)redhat.com&gt; Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; Reviewed-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- src/interface/interface_backend_udev.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/src/interface/interface_backend_udev.c b/src/interface/interface_backend_udev.c index e1a50389c9..48eacdcdc2 100644 --- a/src/interface/interface_backend_udev.c +++ b/src/interface/interface_backend_udev.c @@ -143,12 +143,13 @@ udevGetDevices(struct udev *udev, virUdevStatus status) * * @conn: connection object * @names: optional pointer to array to be filled with interface names - * @names_len: size of @names + * @names_len: size of @names, -1 if only number of interfaces is required (@names is then ignored) * @status: status of interfaces to be listed * @filter: ACL filter function * * Lists interfaces with status matching @status filling them into @names (if - * non-NULL) and returns the number of such interfaces. + * @names_len is positive, caller is expected to pass a properly sized array) + * and returns the number of such interfaces. * * In case of an error -1 is returned and no interfaces are filled into @names. */ @@ -189,7 +190,7 @@ udevListInterfacesByStatus(virConnectPtr conn, g_autoptr(virInterfaceDef) def = NULL; /* Ensure we won't exceed the size of our array */ - if (names && count >= names_len) + if (names_len >= 0 && count >= names_len) break; path = udev_list_entry_get_name(dev_entry); @@ -204,7 +205,8 @@ udevListInterfacesByStatus(virConnectPtr conn, def = udevGetMinimalDefForDevice(dev); if (filter(conn, def)) { - if (names) + /* Fill the array only if caller want's it */ + if (names_len >= 0) names[count] = g_strdup(name); count++; } @@ -224,7 +226,7 @@ udevConnectNumOfInterfaces(virConnectPtr conn) if (virConnectNumOfInterfacesEnsureACL(conn) < 0) return -1; - return udevListInterfacesByStatus(conn, NULL, 0, VIR_UDEV_IFACE_ACTIVE, + return udevListInterfacesByStatus(conn, NULL, -1, VIR_UDEV_IFACE_ACTIVE, virConnectNumOfInterfacesCheckACL); } @@ -247,7 +249,7 @@ udevConnectNumOfDefinedInterfaces(virConnectPtr conn) if (virConnectNumOfDefinedInterfacesEnsureACL(conn) < 0) return -1; - return udevListInterfacesByStatus(conn, NULL, 0, VIR_UDEV_IFACE_INACTIVE, + return udevListInterfacesByStatus(conn, NULL, -1, VIR_UDEV_IFACE_INACTIVE, virConnectNumOfDefinedInterfacesCheckACL); } -- 2.46.0