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Message-ID: <ecdf72c0856f79142af5d951c7cb479cba6c8fb3.camel@ibm.com>
Date: Thu, 4 Sep 2025 18:32:07 +0000
From: Viacheslav Dubeyko <Slava.Dubeyko@....com>
To: Alex Markuze <amarkuze@...hat.com>,
"ceph-devel@...r.kernel.org"
<ceph-devel@...r.kernel.org>
CC: "idryomov@...il.com" <idryomov@...il.com>,
"linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] ceph/inode: drop extra reference from
ceph_get_reply_dir() in ceph_fill_trace()
On Thu, 2025-09-04 at 10:12 +0000, Alex Markuze wrote:
> ceph_get_reply_dir() may return a different, referenced inode when r_parent is stale and the parent directory lock is not held.
> ceph_fill_trace() used that inode but failed to drop the reference when it differed from req->r_parent, leaking an inode reference.
>
> Keep the directory inode in a local and iput() it at function end if it does not match req->r_parent.
I assume that you mean "in a local variable"?
>
> Signed-off-by: Alex Markuze <amarkuze@...hat.com>
> ---
> fs/ceph/inode.c | 30 +++++++++++++++++++-----------
> 1 file changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 470ee595ecf2..cffa2cd7b530 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -1584,6 +1584,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> struct ceph_vino tvino, dvino;
> struct ceph_fs_client *fsc = ceph_sb_to_fs_client(sb);
> struct ceph_client *cl = fsc->client;
> + struct inode *parent_dir = NULL;
> int err = 0;
>
> doutc(cl, "%p is_dentry %d is_target %d\n", req,
> @@ -1601,9 +1602,13 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> * r_parent may be stale, in cases when R_PARENT_LOCKED is not set,
> * so we need to get the correct inode
> */
> - struct inode *dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);
> - if (dir) {
> - err = ceph_fill_inode(dir, NULL, &rinfo->diri,
> + parent_dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);
> + if (unlikely(IS_ERR(parent_dir))) {
> + err = PTR_ERR(parent_dir);
> + goto done;
> + }
> + if (parent_dir) {
> + err = ceph_fill_inode(parent_dir, NULL, &rinfo->diri,
> rinfo->dirfrag, session, -1,
> &req->r_caps_reservation);
> if (err < 0)
> @@ -1612,14 +1617,14 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> WARN_ON_ONCE(1);
> }
>
> - if (dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&
> + if (parent_dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&
> test_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags) &&
> !test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
> bool is_nokey = false;
> struct qstr dname;
> struct dentry *dn, *parent;
> struct fscrypt_str oname = FSTR_INIT(NULL, 0);
> - struct ceph_fname fname = { .dir = dir,
> + struct ceph_fname fname = { .dir = parent_dir,
> .name = rinfo->dname,
> .ctext = rinfo->altname,
> .name_len = rinfo->dname_len,
> @@ -1628,10 +1633,10 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> BUG_ON(!rinfo->head->is_target);
> BUG_ON(req->r_dentry);
>
> - parent = d_find_any_alias(dir);
> + parent = d_find_any_alias(parent_dir);
> BUG_ON(!parent);
>
> - err = ceph_fname_alloc_buffer(dir, &oname);
> + err = ceph_fname_alloc_buffer(parent_dir, &oname);
> if (err < 0) {
> dput(parent);
> goto done;
> @@ -1640,7 +1645,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> err = ceph_fname_to_usr(&fname, NULL, &oname, &is_nokey);
> if (err < 0) {
> dput(parent);
> - ceph_fname_free_buffer(dir, &oname);
> + ceph_fname_free_buffer(parent_dir, &oname);
> goto done;
> }
> dname.name = oname.name;
> @@ -1659,7 +1664,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> dname.len, dname.name, dn);
> if (!dn) {
> dput(parent);
> - ceph_fname_free_buffer(dir, &oname);
> + ceph_fname_free_buffer(parent_dir, &oname);
> err = -ENOMEM;
> goto done;
> }
> @@ -1674,12 +1679,12 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> ceph_snap(d_inode(dn)) != tvino.snap)) {
> doutc(cl, " dn %p points to wrong inode %p\n",
> dn, d_inode(dn));
> - ceph_dir_clear_ordered(dir);
> + ceph_dir_clear_ordered(parent_dir);
> d_delete(dn);
> dput(dn);
> goto retry_lookup;
> }
> - ceph_fname_free_buffer(dir, &oname);
> + ceph_fname_free_buffer(parent_dir, &oname);
>
> req->r_dentry = dn;
> dput(parent);
> @@ -1869,6 +1874,9 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
> &dvino, ptvino);
> }
> done:
> + /* Drop extra ref from ceph_get_reply_dir() if it returned a new inode */
> + if (unlikely(!IS_ERR_OR_NULL(parent_dir) && parent_dir != req->r_parent))
The '&&' implies to check both conditions. However, if we have parent_dir equal
to NULL or some error code, then it doesn't make sense to check the second
condition. I don't think that it could introduce some issue here. But,
potentially, it could be the reason of rarely triggered and non-trivial issue.
What do you think? Do I have point here?
What if we can do like this:
parent_dir = parent_dir != req->r_parent ? parent_dir : NULL;
if (parent_dir)
iput(parent_dir);
> + iput(parent_dir);
Potentially, we could jump here if we have the error.
> doutc(cl, "done err=%d\n", err);
> return err;
> }
Mostly, looks good.
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@....com>
Thanks,
Slava.
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