9.1-stable crashes while copying data from a NFS mounted directory

[Konstantin Belousov]

On Thu, Jan 24, 2013 at 07:50:49PM +0100, Christian Gusenbauer wrote:
> On Thursday 24 January 2013 19:07:23 Konstantin Belousov wrote:
> > On Thu, Jan 24, 2013 at 08:03:59PM +0200, Konstantin Belousov wrote:
> > > On Thu, Jan 24, 2013 at 06:05:57PM +0100, Christian Gusenbauer wrote:
> > > > Hi!
> > > > 
> > > > I'm using 9.1 stable svn revision 245605 and I get the panic below if I
> > > > execute the following commands (as single user):
> > > > 
> > > > # swapon -a
> > > > # dumpon /dev/ada0s3b
> > > > # mount -u /
> > > > # ifconfig age0 inet 192.168.2.2 mtu 6144 up
> > > > # mount -t nfs -o rsize=32768 data:/multimedia /mnt
> > > > # cp /mnt/Movies/test/a.m2ts /tmp
> > > > 
> > > > then the system panics almost immediately. I'll attach the stack trace.
> > > > 
> > > > Note, that I'm using jumbo frames (6144 byte) on a 1Gbit network, maybe
> > > > that's the cause for the panic, because the bcopy (see stack frame
> > > > #15) fails.
> > > > 
> > > > Any clues?
> > > 
> > > I tried a similar operation with the nfs mount of rsize=32768 and mtu
> > > 6144, but the machine runs HEAD and em instead of age. I was unable to
> > > reproduce the panic on the copy of the 5GB file from nfs mount.
> 
> Hmmm, I did a quick test. If I do not change the MTU, so just configuring age0 
> with
> 
> # ifconfig age0 inet 192.168.2.2 up
> 
> then I can copy all files from the mounted directory without any problems, 
> too. So it's probably age0 related?
From your backtrace and the buffer printout, I see somewhat strange thing.
The buffer data address is 0xffffff8171418000, while kernel faulted
at the attempt to write at 0xffffff8171413000, which is is lower then
the buffer data pointer, at the attempt to bcopy to the buffer.

The other data suggests that there were no overflow of the data from the
server response. So it might be that mbuf_len(mp) returned negative number ?
I am not sure is it possible at all.

Try this debugging patch, please. You need to add INVARIANTS etc to the
kernel config.

diff --git a/sys/fs/nfs/nfs_commonsubs.c b/sys/fs/nfs/nfs_commonsubs.c
index efc0786..9a6bda5 100644
--- a/sys/fs/nfs/nfs_commonsubs.c
+++ b/sys/fs/nfs/nfs_commonsubs.c
@@ -218,6 +218,7 @@ nfsm_mbufuio(struct nfsrv_descript *nd, struct uio *uiop, int siz)
 				}
 				mbufcp = NFSMTOD(mp, caddr_t);
 				len = mbuf_len(mp);
+				KASSERT(len > 0, ("len %d", len));
 			}
 			xfer = (left > len) ? len : left;
 #ifdef notdef
@@ -239,6 +240,8 @@ nfsm_mbufuio(struct nfsrv_descript *nd, struct uio *uiop, int siz)
 			uiop->uio_resid -= xfer;
 		}
 		if (uiop->uio_iov->iov_len <= siz) {
+			KASSERT(uiop->uio_iovcnt > 1, ("uio_iovcnt %d",
+			    uiop->uio_iovcnt));
 			uiop->uio_iovcnt--;
 			uiop->uio_iov++;
 		} else {

I thought that server have returned too long response, but it seems to
be not the case from your data. Still, I think the patch below might be
due.

diff --git a/sys/fs/nfsclient/nfs_clrpcops.c b/sys/fs/nfsclient/nfs_clrpcops.c
index be0476a..a89b907 100644
--- a/sys/fs/nfsclient/nfs_clrpcops.c
+++ b/sys/fs/nfsclient/nfs_clrpcops.c
@@ -1444,7 +1444,7 @@ nfsrpc_readrpc(vnode_t vp, struct uio *uiop, struct ucred *cred,
 			NFSM_DISSECT(tl, u_int32_t *, NFSX_UNSIGNED);
 			eof = fxdr_unsigned(int, *tl);
 		}
-		NFSM_STRSIZ(retlen, rsize);
+		NFSM_STRSIZ(retlen, len);
 		error = nfsm_mbufuio(nd, uiop, retlen);
 		if (error)
 			goto nfsmout;
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