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bt: stop the sdp memory allocation craziness

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Clang static analyzer reports a memory leak.  Actually, the allocated
memory escapes here:

        record->attribute_list[record->attributes].pair = data;

but clang is correct that the memory might leak if len is zero.  We
know it isn't; assert that it is the case.

The craziness doesn't end there.  The memory is freed by
bt_l2cap_sdp_close_ch:

       g_free(sdp->service_list[i].attribute_list->pair);

which actually should have been written like this:

       g_free(sdp->service_list[i].attribute_list[0].pair);

The attribute_list is sorted with qsort; but indeed the first
entry of attribute_list should point to "data" even after the qsort,
because the first record has id SDP_ATTR_RECORD_HANDLE, whose
numeric value is zero.

But hang on.  The qsort function is

    static int sdp_attributeid_compare(
                const struct sdp_service_attribute_s *a,
                const struct sdp_service_attribute_s *b)
    {
        return (int) b->attribute_id - a->attribute_id;
    }

but no one ever writes attribute_id.  So it only works if qsort is
stable, and who knows what else is broken, but we can fix it by
setting attribute_id in the while loop.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-07-27 16:47:08 +02:00
parent f5aa69bdc3
commit 393c13b940
1 changed files with 13 additions and 4 deletions
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17
hw/bt/sdp.c
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@ -580,7 +580,7 @@ static void bt_l2cap_sdp_close_ch(void *opaque)
int i;
for (i = 0; i < sdp->services; i ++) {
g_free(sdp->service_list[i].attribute_list->pair);
g_free(sdp->service_list[i].attribute_list[0].pair);
g_free(sdp->service_list[i].attribute_list);
g_free(sdp->service_list[i].uuid);
}
@ -720,6 +720,8 @@ static void sdp_service_record_build(struct sdp_service_record_s *record,
len += sdp_attr_max_size(&def->attributes[record->attributes ++].data,
&record->uuids);
}
assert(len > 0);
record->uuids = pow2ceil(record->uuids);
record->attribute_list =
g_malloc0(record->attributes * sizeof(*record->attribute_list));
@ -730,12 +732,14 @@ static void sdp_service_record_build(struct sdp_service_record_s *record,
record->attributes = 0;
uuid = record->uuid;
while (def->attributes[record->attributes].data.type) {
int attribute_id = def->attributes[record->attributes].id;
record->attribute_list[record->attributes].pair = data;
record->attribute_list[record->attributes].attribute_id = attribute_id;
len = 0;
data[len ++] = SDP_DTYPE_UINT | SDP_DSIZE_2;
data[len ++] = def->attributes[record->attributes].id >> 8;
data[len ++] = def->attributes[record->attributes].id & 0xff;
data[len ++] = attribute_id >> 8;
data[len ++] = attribute_id & 0xff;
len += sdp_attr_write(data + len,
&def->attributes[record->attributes].data, &uuid);
@ -749,10 +753,15 @@ static void sdp_service_record_build(struct sdp_service_record_s *record,
data += len;
}
/* Sort the attribute list by the AttributeID */
/* Sort the attribute list by the AttributeID. The first must be
* SDP_ATTR_RECORD_HANDLE so that bt_l2cap_sdp_close_ch can free
* the buffer.
*/
qsort(record->attribute_list, record->attributes,
sizeof(*record->attribute_list),
(void *) sdp_attributeid_compare);
assert(record->attribute_list[0].pair == data);
/* Sort the searchable UUIDs list for bisection */
qsort(record->uuid, record->uuids,
sizeof(*record->uuid),