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authorJeff Layton <jlayton@kernel.org>2019-04-03 13:16:01 -0400
committerIlya Dryomov <idryomov@gmail.com>2020-01-21 19:02:37 +0100
commit9c1c2b35f1d94de8325344c2777d7ee67492db3b (patch)
tree705fb102b224f7e6685a59945726ed02124479fa /fs/ceph
parentdef9d2780727cec3313ed3522d0123158d87224d (diff)
ceph: hold extra reference to r_parent over life of request
Currently, we just assume that it will stick around by virtue of the submitter's reference, but later patches will allow the syscall to return early and we can't rely on that reference at that point. While I'm not aware of any reports of it, Xiubo pointed out that this may fix a use-after-free. If the wait for a reply times out or is canceled via signal, and then the reply comes in after the syscall returns, the client can end up trying to access r_parent without a reference. Take an extra reference to the inode when setting r_parent and release it when releasing the request. Cc: stable@vger.kernel.org Signed-off-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: "Yan, Zheng" <zyan@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'fs/ceph')
-rw-r--r--fs/ceph/mds_client.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 374db1bd57d1..145d46ba25ae 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -708,8 +708,10 @@ void ceph_mdsc_release_request(struct kref *kref)
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(req->r_inode);
}
- if (req->r_parent)
+ if (req->r_parent) {
ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
+ ceph_async_iput(req->r_parent);
+ }
ceph_async_iput(req->r_target_inode);
if (req->r_dentry)
dput(req->r_dentry);
@@ -2676,8 +2678,10 @@ int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
/* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */
if (req->r_inode)
ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
- if (req->r_parent)
+ if (req->r_parent) {
ceph_get_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
+ ihold(req->r_parent);
+ }
if (req->r_old_dentry_dir)
ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
CEPH_CAP_PIN);