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authorAl Viro <viro@zeniv.linux.org.uk>2018-05-04 08:23:01 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-30 07:50:16 +0200
commit2d2d3f1ee7c4a1fe3bc43b685e16a1439e6821d5 (patch)
treedec8f2d832a3529eb4ca10770052caa0f729275d /fs/dcache.c
parent416808fbc20144d1cb76400d97ddafe26c6df9ff (diff)
do d_instantiate/unlock_new_inode combinations safely
commit 1e2e547a93a00ebc21582c06ca3c6cfea2a309ee upstream. For anything NFS-exported we do _not_ want to unlock new inode before it has grown an alias; original set of fixes got the ordering right, but missed the nasty complication in case of lockdep being enabled - unlock_new_inode() does lockdep_annotate_inode_mutex_key(inode) which can only be done before anyone gets a chance to touch ->i_mutex. Unfortunately, flipping the order and doing unlock_new_inode() before d_instantiate() opens a window when mkdir can race with open-by-fhandle on a guessed fhandle, leading to multiple aliases for a directory inode and all the breakage that follows from that. Correct solution: a new primitive (d_instantiate_new()) combining these two in the right order - lockdep annotate, then d_instantiate(), then the rest of unlock_new_inode(). All combinations of d_instantiate() with unlock_new_inode() should be converted to that. Cc: stable@kernel.org # 2.6.29 and later Tested-by: Mike Marshall <hubcap@omnibond.com> Reviewed-by: Andreas Dilger <adilger@dilger.ca> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 2225b9855c5f..86b578c3ef8b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1859,6 +1859,28 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
}
EXPORT_SYMBOL(d_instantiate);
+/*
+ * This should be equivalent to d_instantiate() + unlock_new_inode(),
+ * with lockdep-related part of unlock_new_inode() done before
+ * anything else. Use that instead of open-coding d_instantiate()/
+ * unlock_new_inode() combinations.
+ */
+void d_instantiate_new(struct dentry *entry, struct inode *inode)
+{
+ BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
+ BUG_ON(!inode);
+ lockdep_annotate_inode_mutex_key(inode);
+ security_d_instantiate(entry, inode);
+ spin_lock(&inode->i_lock);
+ __d_instantiate(entry, inode);
+ WARN_ON(!(inode->i_state & I_NEW));
+ inode->i_state &= ~I_NEW;
+ smp_mb();
+ wake_up_bit(&inode->i_state, __I_NEW);
+ spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL(d_instantiate_new);
+
/**
* d_instantiate_no_diralias - instantiate a non-aliased dentry
* @entry: dentry to complete