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Patch in this message | | | From | "Levin, Alexander (Sasha Levin)" <> | Subject | [GIT PULL for-4.9 35/48] ceph: clean up unsafe d_parent accesses in build_dentry_path | Date | Wed, 11 Oct 2017 00:45:28 +0000 |
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From: Jeff Layton <jlayton@redhat.com>
[ Upstream commit c6b0b656ca24ede6657abb4a2cd910fa9c1879ba ]
While we hold a reference to the dentry when build_dentry_path is called, we could end up racing with a rename that changes d_parent. Handle that situation correctly, by using the rcu_read_lock to ensure that the parent dentry and inode stick around long enough to safely check ceph_snap and ceph_ino.
Link: http://tracker.ceph.com/issues/18148 Signed-off-by: Jeff Layton <jlayton@redhat.com> Reviewed-by: Yan, Zheng <zyan@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> --- fs/ceph/mds_client.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index e3e1a80b351e..c0f52c443c34 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -1782,13 +1782,18 @@ static int build_dentry_path(struct dentry *dentry, int *pfreepath) { char *path; + struct inode *dir; - if (ceph_snap(d_inode(dentry->d_parent)) == CEPH_NOSNAP) { - *pino = ceph_ino(d_inode(dentry->d_parent)); + rcu_read_lock(); + dir = d_inode_rcu(dentry->d_parent); + if (dir && ceph_snap(dir) == CEPH_NOSNAP) { + *pino = ceph_ino(dir); + rcu_read_unlock(); *ppath = dentry->d_name.name; *ppathlen = dentry->d_name.len; return 0; } + rcu_read_unlock(); path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1); if (IS_ERR(path)) return PTR_ERR(path); -- 2.11.0
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