On Mon, 2021-06-21 at 12:51 +0100, Luis Henriques wrote:
> On Fri, Jun 18, 2021 at 01:39:59PM -0400, Jeff Layton wrote:
> > Currently, we set the r_parent pointer but then don't take a reference
> > to it until we submit the request. If we end up freeing the req before
> > that point, then we'll do a iput when we shouldn't.
> >
> > Instead, take the inode reference in the callers, so that it's always
> > safe to call ceph_mdsc_put_request on the req, even before submission.
> >
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/ceph/dir.c | 9 +++++++++
> > fs/ceph/export.c | 1 +
> > fs/ceph/file.c | 1 +
> > fs/ceph/mds_client.c | 1 -
> > 4 files changed, 11 insertions(+), 1 deletion(-)
> >
> > Note that this isn't a problem with the existing code, because we never
> > put the last reference before submission, but with the coming fscrypt
> > patchset, we can end up doing this and this becomes a problem. With ths
> > change, a set r_parent field means a reference *was* taken.
> >
> > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> > index bd508b1aeac2..a656c5c00e65 100644
> > --- a/fs/ceph/dir.c
> > +++ b/fs/ceph/dir.c
> > @@ -788,6 +788,7 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
> > mask |= CEPH_CAP_XATTR_SHARED;
> > req->r_args.getattr.mask = cpu_to_le32(mask);
> >
> > + ihold(dir);
> > req->r_parent = dir;
>
> Other than my OCD saying that these two statements should be in the
> reverse order (or maybe all the other should...?), feel free to add my
>
> Reviewed-by: Luis Henriques <lhenriques@xxxxxxx>
>
Thanks. I sort of wish ihold() returned the inode pointer to make this
sort of thing more clear, but changing it now would probably be painful.
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > err = ceph_mdsc_do_request(mdsc, NULL, req);
> > @@ -861,6 +862,7 @@ static int ceph_mknod(struct user_namespace *mnt_userns, struct inode *dir,
> > req->r_dentry = dget(dentry);
> > req->r_num_caps = 2;
> > req->r_parent = dir;
> > + ihold(dir);
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_args.mknod.mode = cpu_to_le32(mode);
> > req->r_args.mknod.rdev = cpu_to_le32(rdev);
> > @@ -922,6 +924,8 @@ static int ceph_symlink(struct user_namespace *mnt_userns, struct inode *dir,
> > goto out;
> > }
> > req->r_parent = dir;
> > + ihold(dir);
> > +
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_dentry = dget(dentry);
> > req->r_num_caps = 2;
> > @@ -986,6 +990,7 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
> > req->r_dentry = dget(dentry);
> > req->r_num_caps = 2;
> > req->r_parent = dir;
> > + ihold(dir);
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_args.mkdir.mode = cpu_to_le32(mode);
> > req->r_dentry_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_AUTH_EXCL;
> > @@ -1030,6 +1035,7 @@ static int ceph_link(struct dentry *old_dentry, struct inode *dir,
> > req->r_num_caps = 2;
> > req->r_old_dentry = dget(old_dentry);
> > req->r_parent = dir;
> > + ihold(dir);
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
> > req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
> > @@ -1151,6 +1157,7 @@ static int ceph_unlink(struct inode *dir, struct dentry *dentry)
> > req->r_dentry = dget(dentry);
> > req->r_num_caps = 2;
> > req->r_parent = dir;
> > + ihold(dir);
> > req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
> > req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
> > req->r_inode_drop = ceph_drop_caps_for_unlink(inode);
> > @@ -1225,6 +1232,7 @@ static int ceph_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> > req->r_old_dentry = dget(old_dentry);
> > req->r_old_dentry_dir = old_dir;
> > req->r_parent = new_dir;
> > + ihold(new_dir);
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_old_dentry_drop = CEPH_CAP_FILE_SHARED;
> > req->r_old_dentry_unless = CEPH_CAP_FILE_EXCL;
> > @@ -1721,6 +1729,7 @@ static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)
> > req->r_dentry = dget(dentry);
> > req->r_num_caps = 2;
> > req->r_parent = dir;
> > + ihold(dir);
> >
> > mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
> > if (ceph_security_xattr_wanted(dir))
> > diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> > index 65540a4429b2..1d65934c1262 100644
> > --- a/fs/ceph/export.c
> > +++ b/fs/ceph/export.c
> > @@ -542,6 +542,7 @@ static int ceph_get_name(struct dentry *parent, char *name,
> > ihold(inode);
> > req->r_ino2 = ceph_vino(d_inode(parent));
> > req->r_parent = d_inode(parent);
> > + ihold(req->r_parent);
> > set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> > req->r_num_caps = 2;
> > err = ceph_mdsc_do_request(mdsc, NULL, req);
> > diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> > index d3874c2df4b1..c8fd11cf4510 100644
> > --- a/fs/ceph/file.c
> > +++ b/fs/ceph/file.c
> > @@ -706,6 +706,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
> > mask |= CEPH_CAP_XATTR_SHARED;
> > req->r_args.open.mask = cpu_to_le32(mask);
> > req->r_parent = dir;
> > + ihold(dir);
> >
> > if (flags & O_CREAT) {
> > struct ceph_file_layout lo;
> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > index c03098c58be3..52ae5373437d 100644
> > --- a/fs/ceph/mds_client.c
> > +++ b/fs/ceph/mds_client.c
> > @@ -2983,7 +2983,6 @@ int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
> > ceph_take_cap_refs(ci, CEPH_CAP_PIN, false);
> > __ceph_touch_fmode(ci, mdsc, fmode);
> > spin_unlock(&ci->i_ceph_lock);
> > - ihold(req->r_parent);
> > }
> > if (req->r_old_dentry_dir)
> > ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
> > --
> > 2.31.1
> >
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
