From f2126dbc1dcaca92250427e76e7a87e61b10f540 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Wed, 13 Feb 2019 16:51:22 +0100

Subject: [PATCH] sd-bus: if we receive an invalid dbus message, ignore and

 proceeed

dbus-daemon might have a slightly different idea of what a valid msg is

than us (for example regarding valid msg and field sizes). Let's hence

try to proceed if we can and thus drop messages rather than fail the

connection if we fail to validate a message.

Hopefully the differences in what is considered valid are not visible

for real-life usecases, but are specific to exploit attempts only.

(cherry-picked from commit 6d586a13717ae057aa1b4127400c3de61cd5b9e7)

Related: #1667871

---

 src/libsystemd/sd-bus/bus-socket.c | 9 ++++++---

 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c

index ab56ef4f3..4437024bb 100644

--- a/src/libsystemd/sd-bus/bus-socket.c

+++ b/src/libsystemd/sd-bus/bus-socket.c

@@ -879,7 +879,7 @@ static int bus_socket_read_message_need(sd_bus *bus, size_t *need) {

 }

 static int bus_socket_make_message(sd_bus *bus, size_t size) {

-        sd_bus_message *t;

+        sd_bus_message *t = NULL;

         void *b;

         int r;

@@ -905,7 +905,9 @@ static int bus_socket_make_message(sd_bus *bus, size_t size) {

                                     NULL,

                                     NULL,

                                     &t);

-        if (r < 0) {

+        if (r == -EBADMSG)

+                log_debug_errno(r, "Received invalid message from connection %s, dropping.", strna(bus->description));

+        else if (r < 0) {

                 free(b);

                 return r;

         }

@@ -916,7 +918,8 @@ static int bus_socket_make_message(sd_bus *bus, size_t size) {

         bus->fds = NULL;

         bus->n_fds = 0;

-        bus->rqueue[bus->rqueue_size++] = t;

+        if (t)

+                bus->rqueue[bus->rqueue_size++] = t;

         return 1;

 }