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>
Cheers,
--
Luís
> 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
>
