Lock leakage on rename if vop->vop_rename is NULL (kern/107439)

Kostik Belousov kostikbel at gmail.com
Fri Apr 2 09:04:06 UTC 2010


[Do not want to get "YOU ARE NOT IN WHITELIST" garbage]

On Fri, Apr 02, 2010 at 10:10:02AM +0300, Mikolaj Golub wrote:
> Hi,
> 
> Could somebody look at kern/107439? Although the pr is closed the issue still
> persists: if a file system does not provide vop_rename the vop_bypass() is
> called and the vnods, which are expected to be unlocked in VOP_RENAME(), are
> left locked.
> 
> I have attached there the patch that solves the problem but I am not confident
> about the solution.

Patch seems to be eaten by unnamed daemon, but survived in the PR log.
I think that ap->ap_tvp should be handled too.

Anyway, I assume that the proper solution there would be to implement
default vop_rename that is in fact identical to deadfs_rename(). The
later exists exactly to handle a very similar situation.

Please test the patch below. If it works for you, I will combine
deadfs_rename() and vop_norename().

Thanks for the report and patch.

diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index 50bf0d2..7e278a5 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -67,6 +67,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/vnode_pager.h>
 
 static int	vop_nolookup(struct vop_lookup_args *);
+static int	vop_norename(struct vop_rename_args *);
 static int	vop_nostrategy(struct vop_strategy_args *);
 static int	get_next_dirent(struct vnode *vp, struct dirent **dpp,
 				char *dirbuf, int dirbuflen, off_t *off,
@@ -113,6 +114,7 @@ struct vop_vector default_vnodeops = {
 	.vop_poll =		vop_nopoll,
 	.vop_putpages =		vop_stdputpages,
 	.vop_readlink =		VOP_EINVAL,
+	.vop_rename =		vop_norename,
 	.vop_revoke =		VOP_PANIC,
 	.vop_strategy =		vop_nostrategy,
 	.vop_unlock =		vop_stdunlock,
@@ -206,6 +208,27 @@ vop_nolookup(ap)
 }
 
 /*
+ * vop_norename:
+ *
+ * Handle unlock and reference counting for arguments of vop_rename
+ * for filesystems that do not implement rename operation.
+ */
+static int
+vop_norename(struct vop_rename_args *ap)
+{
+
+	if (ap->a_tvp != NULL)
+		vput(ap->a_tvp);
+	if (ap->a_tdvp == ap->a_tvp)
+		vrele(ap->a_tdvp);
+	else
+		vput(ap->a_tdvp);
+	vrele(ap->a_fdvp);
+	vrele(ap->a_fvp);
+	return (EOPNOTSUPP);
+}
+
+/*
  *	vop_nostrategy:
  *
  *	Strategy routine for VFS devices that have none.
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