More netbsd32 emulation ktrace overrides

[Martin Husemann]

As mentioned in the other thread here, I am trying to make ktrace output
working for netbsd32 emulated ktrace/kdump.

The patch below allows emulations to override the "msghdr" ktrace data
output by various variants of sendmsg/recvmsg. This is simmply done by
passing two new args to do_sys_sendmsg()/do_sys_recvmsg() and friends
which provide alternative data to record in the ktrace record.

Since a full msgheader is not always conveniently available, it is also
possible to pass a NULL pointer and ~0U as size to skip this ktrace
record completely.

If passing NULL/0 as the new args, the native msghdr is output, which means
most callers simply needed adding "NULL, 0," in the argument list.

A few compat versions are missing here, but will be added before commit.

Any objections?

Martin

[William J. Coldwell]

Are these overflows a security issue?
Like giving up valid kernel memory.

--
Cryo:William J. Coldwell ARIN:WC25/AS7769 PGP:0xF97CC215/0x5E9944455
Warped, Inc. warped.com Founder/CTO 661-WARPED1 @warped @deadjournal
NetBSD netbsd.org/pkgsrc.org President,Project Security,Social Media
"Put on 3D glasses, otherwise you only see in 1½D.” [self opinion];

> <ktr_recvsend.patch>

[Martin Husemann]

On Fri, Sep 09, 2016 at 04:00:56AM -0500, William J. Coldwell wrote:
> Are these overflows a security issue?
> Like giving up valid kernel memory.

No security issue. They just record the 64bit version of the msghdr
structure (which has just been passed in from userland anyway) instead
of the 32bit one, and the decoder in kdump can not handle that.

Martin

[William J. Coldwell]

Thank you for clarifying.

--
Cryo:William J. Coldwell ARIN:WC25/AS7769 PGP:0xF97CC215/0x5E9944455
Warped, Inc. warped.com Founder/CTO 661-WARPED1 @warped @deadjournal
NetBSD netbsd.org/pkgsrc.org President,Project Security,Social Media
"Put on 3D glasses, otherwise you only see in 1½D.” [self opinion];