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Safer nfsd_cross_mnt()

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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 <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2009-04-18 02:32:31 -04:00
parent e5d67f0715
commit 1644ccc8a9
1 changed files with 7 additions and 2 deletions
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9
fs/nfsd/vfs.c
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@ -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);