Date: Fri, 27 Jun 1997 12:10:47 -0700 (PDT) From: Bill Paul <wpaul@FreeBSD.ORG> To: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG, cvs-sys@FreeBSD.ORG Subject: cvs commit: src/sys/nfs nfs_vfsops.c Message-ID: <199706271910.MAA10921@freefall.freebsd.org>
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wpaul 1997/06/27 12:10:47 PDT Modified files: sys/nfs nfs_vfsops.c Log: Fix a condition where nfs_statfs() can precipitate a panic. There is code that says this: nfsm_request(vp, NFSPROC_FSSTAT, p, cred); if (v3) nfsm_postop_attr(vp, retattr); if (!error) nfsm_dissect(sfp, struct nfs_statfs *, NFSX_STATFS(v3)); The problem here is that if error != 0, nfsm_dissect() will not be called, which leaves sfp == NULL. But nfs_statfs() does not bail out at this point: it continues processing until it tries to dereference sfp, which causes a panic. I was able to generate this crash under the following conditions: 1) Set up a machine as an NFS server and NFS client, with amd running (using NIS maps). /usr/local is exported, though any exported fs can can be used to trigger the bug. 2) Log in as normal user, with home directory mounted from a SunOS 4.1.3 NFS server via amd (along with a few other NFS filesystems from same machine). 3) Su to root and type the following: # mount localhost:/usr/local /mnt # df To fix the panic, I changed the code to read: if (!error) { nfsm_dissect(sfp, struct nfs_statfs *, NFSX_STATFS(v3)); } else goto nfsmout; This is a bit kludgy in that nfsmout is a label defined by the nfsm_subs.h macros, but these macros are themselves more than a little kludgy. This stops the machine from crashing, but does not fix the overall bug: 'error' somehow becomes 5 (EIO) when a statfs() is performed on the locally mounted NFS filesystem. This seems to only happen the first time the filesystem is accesed: on subsequent accesses, it seems to work fine again. Now, I know there's no practical use in mounting a local filesystem via NFS, but doing it shouldn't cause the system to melt down. Revision Changes Path 1.44 +5 -2 src/sys/nfs/nfs_vfsops.c
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