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fs: fix dropping of rcu-walk from force_reval_path 

As J. R. Okajima noted, force_reval_path passes in the same dentry to
d_revalidate as the one in the nameidata structure (other callers pass in a
child), so the locking breaks. This can oops with a chrooted nfs mount, for
example. Similarly there can be other problems with revalidating a dentry
which is already in nameidata of the path walk.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-14 02:36:19 +00:00 committed by Nick Piggin
parent bb20c18db6
commit 90dbb77ba4
1 changed files with 8 additions and 0 deletions
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8
fs/namei.c
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@ -479,6 +479,14 @@ static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
/*
* It can be possible to revalidate the dentry that we started
* the path walk with. force_reval_path may also revalidate the
* dentry already committed to the nameidata.
*/
if (unlikely(parent == dentry))
return nameidata_drop_rcu(nd);
BUG_ON(!(nd->flags & LOOKUP_RCU));
if (nd->root.mnt) {
spin_lock(&fs->lock);