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authorAl Viro <viro@zeniv.linux.org.uk>2009-04-18 02:32:31 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2009-04-20 23:01:15 -0400
commit1644ccc8a99ae73859c39372f96afdbf03c9f80d (patch)
tree27b568d2fcc00738a505fd562d7fa4728aa43d7f /fs/nfsd
parente5d67f0715bc60f6c19abdd86d007d7bb29c9951 (diff)
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 <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/nfsd')
-rw-r--r--fs/nfsd/vfs.c9
1 files changed, 7 insertions, 2 deletions
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);