Re: [libvirt] [PATCH 01/11] tlscontext: Make sure to get proper pointer to name
On 01/31/2013 11:41 AM, Eric Blake wrote:
On 01/31/2013 03:44 AM, Osier Yang wrote:
> On 2013年01月31日 03:36, John Ferlan wrote:
>> The 'dname' string was only filled in within the loop when available;
>> however, the TRACE macros used it unconditionally and caused Coverity
>> to compain about BAD_SIZEOF. Using a dnameptr keeps Coverity at bay and
s/compain/complain/
fixed this... fingers don't always type what the brain tells them to :-)
>> makes sure dname was properly filled before attempting the
TRACE message.
>> ---
>> src/rpc/virnettlscontext.c | 8 +++++---
>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> @@ -950,6 +950,7 @@ static int
>> virNetTLSContextValidCertificate(virNetTLSContextPtr ctxt,
>> unsigned int nCerts, i;
>> char dname[256];
>> size_t dnamesize = sizeof(dname);
>> + char *dnameptr = NULL;
Would it be any simpler to just 0-initialize dname, as in:
char dname[256] = "";
As Osier points out there is a memset(dname, 0, dnamesize) in the code
Changing the code to use the above still results in Coverity complaint
for each PROBE:
1062
(1) Event bad_sizeof: Taking the size of "dname", which is the address
of an object, is suspicious. Did you intend the size of the object itself?
1063 PROBE(RPC_TLS_CONTEXT_SESSION_ALLOW,
1064 "ctxt=%p sess=%p dname=%s",
1065 ctxt, sess, dname);
This is the only PROBE I found using a stack buffer of a specific size.
If I changed the code to VIR_ALLOC_N(dname, dnamesize);, then the
message goes away too.
I believe the 256 was chosen since that the max length of a
distinguished name field from what I've read
>>
>> PROBE(RPC_TLS_CONTEXT_SESSION_ALLOW,
>> "ctxt=%p sess=%p dname=%s",
>> - ctxt, sess, dname);
At which point, the PROBE(..., dname) would be guaranteed to have a NUL
terminator within range? If I understand it, Coverity is complaining
that if dname is uninitialized, then the PROBE() may read beyond 256
bytes while looking for the end of a string.
>
> I guess dname[0] is guaranteed to be not nul as long as
> gnutls_x509_crt_get_dn succeeded.
Not unless we pre-initialize dname[0].
>
> If so, the patch can be simplified as:
>
> dname[0] ? dname : "(unknown)"
Using a conditional would make the difference between a probe stating
'dname=' vs. 'dname=(unknown)'; I don't think it adds that much to
need
a ternary ?: in the PROBE.