reproducible panic in netisr
Julian Elischer
julian at elischer.org
Thu Aug 6 15:10:23 UTC 2009
Rick Macklem wrote:
>
>
> On Thu, 6 Aug 2009, Robert Watson wrote:
>
>> other places where we have very strong alignment requirements on
>> i386/amd64, such as the td_ucred pointer that we check for change on
>> system calls/traps to see if we need to refresh the thread's
>> credential from the process credential.
>>
> Does this imply that the nfs/krpc hack of:
> oldcred = td->td_ucred;
> td->td_ucred = "some other cred ptr"
> ...
> td->td_ucred = oldcred;
>
> could be dangerous?
>
> Maybe it should be converted to code that replaces the contents instead
> of replacing the *cred? (Variants of the above live in a bunch of places
> in the krpc, nlm and nfs code, due to the fact that the socket functions
> use td->td_ucred in various places.)
no, creds are read-only .. you never change a cred.
You alwasy make a new one ans use it, becasue you may be shareing your
cred with hundreds of other sibling threads or processes. (they are
refcounted)
>
> rick
>
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