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authorDaniel Stenberg <daniel@haxx.se>2007-07-14 13:11:36 +0000
committerDaniel Stenberg <daniel@haxx.se>2007-07-14 13:11:36 +0000
commit7fc300d5dc8e355b410f9810e4550a7b36c170f5 (patch)
tree55484b8d0a7f802d1ccc05b38a5a23aea82cbf8d /ares/CHANGES
parent88ce03e94507d009edb0bb80e778fb8ad69eb6ac (diff)
added Vlad's entire description of his valgrind fix
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* July 14 2007 (Daniel Stenberg)
-- Vlad Dinulescu fixed two outstanding valgrind reports.
+- Vlad Dinulescu fixed two outstanding valgrind reports:
+
+
+ 1. In ares_query.c , in find_query_by_id we compare q->qid (which is a short
+ int variable) with qid, which is declared as an int variable. Moreover,
+ DNS_HEADER_SET_QID is used to set the value of qid, but DNS_HEADER_SET_QID
+ sets only the first two bytes of qid. I think that qid should be declared as
+ "unsigned short" in this function.
+
+ 2. The same problem occurs in ares_process.c, process_answer() . query->qid
+ (an unsigned short integer variable) is compared with id, which is an
+ integer variable. Moreover, id is initialized from DNS_HEADER_QID which sets
+ only the first two bytes of id. I think that the id variable should be
+ declared as "unsigned short" in this function.
+
+ Even after declaring these variables as "unsigned short", the valgrind
+ errors are still there. Which brings us to the third problem.
+
+ 3. The third problem is that Valgrind assumes that query->qid is not
+ initialised correctly. And it does that because query->qid is set from
+ DNS_HEADER_QID(qbuf); Valgrind says that qbuf has unitialised bytes. And
+ qbuf has uninitialised bytes because of channel->next_id . And next_id is
+ set by ares_init.c:ares__generate_new_id() . I found that putting short r=0
+ in this function (instead of short r) makes all Valgrind warnings go away.
+ I have studied ares__rc4() too, and this is the offending line:
+
+ buffer_ptr[counter] ^= state[xorIndex]; (ares_query.c:62)
+
+ This is what triggers Valgrind.. buffer_ptr is unitialised in this function,
+ and by applying ^= on it, it remains unitialised.
Version 1.4.0 (June 8, 2007)