From 1644ccc8a99ae73859c39372f96afdbf03c9f80d Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 18 Apr 2009 02:32:31 -0400 Subject: Safer nfsd_cross_mnt() AFAICS, we have a subtle bug there: if we have crossed mountpoint *and* it got mount --move'd away, we'll be holding only one reference to fs containing dentry - exp->ex_path.mnt. IOW, we ought to dput() before exp_put(). Signed-off-by: Al Viro --- fs/nfsd/vfs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'fs/nfsd/vfs.c') diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index ab93fcfef25..46e6bd2d4f0 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -116,10 +116,15 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, } if ((exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) { /* successfully crossed mount point */ - exp_put(exp); - *expp = exp2; + /* + * This is subtle: dentry is *not* under mnt at this point. + * The only reason we are safe is that original mnt is pinned + * down by exp, so we should dput before putting exp. + */ dput(dentry); *dpp = mounts; + exp_put(exp); + *expp = exp2; } else { exp_put(exp2); dput(mounts); -- cgit v1.2.3