linprocfs_domtab() rewrite

[trasz]

Summary

Rewrite linprocfs_domtab() as a wrapper around kern_getfsstat(). This
adds missing jail and MAC checks.

[kib]

This is most likely a good change.

sys/compat/linprocfs/linprocfs.c

335 ↗

(On Diff #4562)

Do not initialize in definition.

It is probably safer to initialize the buf to NULL (not required, but it made me wonder for a moment).

342 ↗

(On Diff #4562)

I see that this is not changed, but why is error from namei() ignored ?

[kib]

It seems reasonable to change the kern_getfsstat() to return the count explicitely, instead of relying on td_retval. I think it was only used by compat32 so far, but new use is ugly without the proper handling of count.

[trasz]

Tidy up.

[trasz]

I think the error is ignored to account for possibility that the path doesn't exist. I'd prefer not to touch it for now, this code is a little scary.

As for returning the count from kern_getfsstat() - good point, but I'd rather leave this for later.

[trasz]

So, does it look ok now? If so, can you mark it Accepted? Thanks!

[kib]

I do not like td_retval thing, it is too hackish. IMO this is exactly the right moment to fix it.

I agree that handling namei error (or commenting why error could be ignored) is for the other moment.

[trasz]

Hm, okay. How to return the count, then? Reuse the 'count' argument, or add a new one? Is there a convention that says which argument should it be? The last?

[kib]

In D2193#13, @trasz wrote:

Hm, okay. How to return the count, then? Reuse the 'count' argument, or add a new one? Is there a convention that says which argument should it be? The last?

Up to you and a common sense. I would add the last argument like int *count (exact type might need some correction).

[trasz]

Make kern_getfsstat() return count explicitly.

[kib]

Yes, this is the intended change, but it seems that you missed compat/freebsd32.

[trasz]

Don't miss compat32.

[kib]

sys/compat/freebsd32/freebsd32_misc.c

258 ↗

(On Diff #4813)

Move the assignment after we ensured that all copyout()s succeeded.

sys/kern/vfs_syscalls.c

442 ↗

(On Diff #4813)

Do not assign to td_retval if error != 0.

[trasz]

Fix retval handling.

[kib]

sys/kern/vfs_syscalls.c

635 ↗

(On Diff #4815)

There too ?

[trasz]

Add one more missing error check.

[trasz]

Closed by commit rS281551 (authored by @trasz).