Date: Fri, 3 Feb 2006 10:41:29 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Kostik Belousov <kostikbel@gmail.com>, jeff@freebsd.org Subject: Re: [patch] GIANT and fchdir Message-ID: <200602031041.31576.jhb@freebsd.org> In-Reply-To: <c781d7f30602030448k339fbe69rb641e2ade9d60255@mail.gmail.com> References: <c781d7f30602030448k339fbe69rb641e2ade9d60255@mail.gmail.com>
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On Friday 03 February 2006 07:48, Kostik Belousov wrote: > I have a system where root is on MP-safe UFS, and have (MP-unsafe) > fdescfs mounted at /dev/fd. Doing "find /" causes panic in line 2029 > of the sys/kern/vfs_subr.c, namely, in vrele() assertion > VFS_ASSERT_GIANT(vp->v_mount); > > Trace shows that the guilty process (find) did the fchdir syscall. Reason > for the panic is call vrele(vpold) in kern/vfs_syscalls.c, line 718 without > calling VFS_LOCK_GIANT for vpold. > > Problem is quite similar to what was fixed several days ago for chroot > and chdir. > > The following small patch fixes the panic: > > Index: sys/kern/vfs_syscalls.c > =================================================================== > RCS file: /usr/local/arch/ncvs/src/sys/kern/vfs_syscalls.c,v > retrieving revision 1.402 > diff -u -r1.402 vfs_syscalls.c > --- sys/kern/vfs_syscalls.c 1 Feb 2006 09:30:44 -0000 1.402 > +++ sys/kern/vfs_syscalls.c 3 Feb 2006 12:47:13 -0000 > @@ -715,6 +715,8 @@ > vpold = fdp->fd_cdir; > fdp->fd_cdir = vp; > FILEDESC_UNLOCK_FAST(fdp); > + VFS_UNLOCK_GIANT(vfslocked); > + vfslocked = VFS_LOCK_GIANT(vpold->v_mount); > vrele(vpold); > VFS_UNLOCK_GIANT(vfslocked); > return (0); > > > It seems that the issue is present in 6-STABLE too. Yes, chdir() was just fixed a few days ago. I think Robert Watson has basically the same patch (he drops giant slightly earlier though) that he will commit soon. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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