bus-message: fix calculation of offsets table for arrays

This is similar to the grandparent commit 'fix calculation of offsets table',
except that now the change is for array elements. Same story as before: we need
to make sure that the offsets increase enough taking alignment into account.

While at it, rename 'p' to 'previous' to match similar code in other places.

diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 11b050a..f544ec1 100644 (file)
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -3507,7 +3507,7 @@ static int bus_message_enter_array(
 
         size_t rindex;
         void *q;
-        int r, alignment;
+        int r;
 
         assert(m);
         assert(c);
@@ -3533,6 +3533,7 @@ static int bus_message_enter_array(
 
         if (!BUS_MESSAGE_IS_GVARIANT(m)) {
                 /* dbus1 */
+                int alignment;
 
                 r = message_peek_body(m, &rindex, 4, 4, &q);
                 if (r < 0)
@@ -3566,7 +3567,8 @@ static int bus_message_enter_array(
                 *n_offsets = 0;
 
         } else {
-                size_t where, p = 0, framing, sz;
+                size_t where, previous = 0, framing, sz;
+                int alignment;
                 unsigned i;
 
                 /* gvariant: variable length array */
@@ -3594,17 +3596,22 @@ static int bus_message_enter_array(
                 if (!*offsets)
                         return -ENOMEM;
 
+                alignment = bus_gvariant_get_alignment(c->signature);
+                assert(alignment > 0);
+
                 for (i = 0; i < *n_offsets; i++) {
-                        size_t x;
+                        size_t x, start;
+
+                        start = ALIGN_TO(previous, alignment);
 
                         x = bus_gvariant_read_word_le((uint8_t*) q + i * sz, sz);
                         if (x > c->item_size - sz)
                                 return -EBADMSG;
-                        if (x < p)
+                        if (x < start)
                                 return -EBADMSG;
 
                         (*offsets)[i] = rindex + x;
-                        p = x;
+                        previous = x;
                 }
 
                 *item_size = (*offsets)[0] - rindex;

diff --git a/test/fuzz/fuzz-bus-message/crash-d8f3941c74219b4c03532c9b244d5ea539c61af5 b/test/fuzz/fuzz-bus-message/crash-d8f3941c74219b4c03532c9b244d5ea539c61af5
new file mode 100644 (file)
index 0000000..26262e1
Binary files /dev/null and b/test/fuzz/fuzz-bus-message/crash-d8f3941c74219b4c03532c9b244d5ea539c61af5 differ