Date: Mon, 15 Oct 2001 21:43:55 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: <current@freebsd.org> Cc: <stable@freebsd.org>, <dillon@freebsd.org>, <alfred@freebsd.org> Subject: coredump() broken for nfs filesystems Message-ID: <20011015211333.B576-100000@delplex.bde.org>
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coredump() now usually creates empty core files for nfs filesystems.
This seems to be caused by the changes in rev.1.132 (-current) and
rev.1.72.2.9 (RELENG_4), and braindamage in nfs_dolock():
Index: kern_sig.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_sig.c,v
retrieving revision 1.131
retrieving revision 1.132
diff -u -2 -r1.131 -r1.132
--- kern_sig.c 6 Sep 2001 22:20:41 -0000 1.131
+++ kern_sig.c 8 Sep 2001 20:02:32 -0000 1.132
> ...
@@ -1896,6 +1898,17 @@
NDFREE(&nd, NDF_ONLY_PNBUF);
vp = nd.ni_vp;
+
+ VOP_UNLOCK(vp, 0, p);
+ lf.l_whence = SEEK_SET;
+ lf.l_start = 0;
+ lf.l_len = 0;
+ lf.l_type = F_WRLCK;
+ error = VOP_ADVLOCK(vp, (caddr_t)p, F_SETLK, &lf, F_FLOCK);
+ if (error)
+ goto out2;
+
This usually goes to out2 with error EOPNOTSUPP if the core file is on
an nfs filesystem.
From nfs_dolock():
% /*
% * XXX Hack to temporarily allow this process (regardless of it's creds)
% * to open the fifo we need to write to. vn_open() really should
% * take a ucred (and once it does, this code should be fixed to use
% * proc0's ucred.
% */
% saved_uid = p->p_ucred->cr_uid;
% p->p_ucred->cr_uid = 0; /* temporarly run the vn_open as root */
%
% fmode = FFLAGS(O_WRONLY);
% error = vn_open(&nd, &fmode, 0);
This vn_open() usually fails, because root is usually mapped so has even
less write permission than most users. I don't see how nfs write locks can
work for syscalls either.
% p->p_ucred->cr_uid = saved_uid;
% if (error != 0) {
% return (error == ENOENT ? EOPNOTSUPP : error);
% }
EOPNOTSUPP is a strange error for foot shooting.
Bruce
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