Re: [RFC PATCH v7 11/24] ceph: add routine to create fscrypt context prior to RPC

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2021-07-07 at 11:48 +0100, Luis Henriques wrote:
> On Fri, Jun 25, 2021 at 09:58:21AM -0400, Jeff Layton wrote:
> > After pre-creating a new inode, do an fscrypt prepare on it, fetch a
> > new encryption context and then marshal that into the security context
> > to be sent along with the RPC. Call the new function from
> > ceph_new_inode.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  fs/ceph/crypto.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> >  fs/ceph/crypto.h | 25 +++++++++++++++++++++++++
> >  fs/ceph/inode.c  | 10 ++++++++--
> >  fs/ceph/super.h  |  5 +++++
> >  fs/ceph/xattr.c  |  3 +++
> >  5 files changed, 83 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
> > index 997a33e1d59f..675d41fd2eb0 100644
> > --- a/fs/ceph/crypto.c
> > +++ b/fs/ceph/crypto.c
> > @@ -4,6 +4,7 @@
> >  #include <linux/fscrypt.h>
> >  
> >  #include "super.h"
> > +#include "mds_client.h"
> >  #include "crypto.h"
> >  
> >  static int ceph_crypt_get_context(struct inode *inode, void *ctx, size_t len)
> > @@ -86,3 +87,44 @@ void ceph_fscrypt_set_ops(struct super_block *sb)
> >  {
> >  	fscrypt_set_ops(sb, &ceph_fscrypt_ops);
> >  }
> > +
> > +int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
> > +				 struct ceph_acl_sec_ctx *as)
> > +{
> > +	int ret, ctxsize;
> > +	bool encrypted = false;
> > +	struct ceph_inode_info *ci = ceph_inode(inode);
> > +
> > +	ret = fscrypt_prepare_new_inode(dir, inode, &encrypted);
> > +	if (ret)
> > +		return ret;
> > +	if (!encrypted)
> > +		return 0;
> > +
> > +	as->fscrypt_auth = kzalloc(sizeof(*as->fscrypt_auth), GFP_KERNEL);
> > +	if (!as->fscrypt_auth)
> > +		return -ENOMEM;
> > +
> > +	ctxsize = fscrypt_context_for_new_inode(as->fscrypt_auth->cfa_blob, inode);
> > +	if (ctxsize < 0)
> > +		return ctxsize;
> > +
> > +	as->fscrypt_auth->cfa_version = cpu_to_le32(CEPH_FSCRYPT_AUTH_VERSION);
> > +	as->fscrypt_auth->cfa_blob_len = cpu_to_le32(ctxsize);
> > +
> > +	WARN_ON_ONCE(ci->fscrypt_auth);
> > +	kfree(ci->fscrypt_auth);
> 
> It's odd to have again a kfree() after a WARN_ON_ONCE() :-)
> 

Throw a warning but handle the case sanely? That seems normal to me :)

> > +	ci->fscrypt_auth_len = ceph_fscrypt_auth_size(ctxsize);
> > +	ci->fscrypt_auth = kmemdup(as->fscrypt_auth, ci->fscrypt_auth_len, GFP_KERNEL);
> > +	if (!ci->fscrypt_auth)
> > +		return -ENOMEM;
> > +
> > +	inode->i_flags |= S_ENCRYPTED;
> > +
> > +	return 0;
> > +}
> > +
> > +void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req, struct ceph_acl_sec_ctx *as)
> > +{
> > +	swap(req->r_fscrypt_auth, as->fscrypt_auth);
> > +}
> 
> This means that req->r_fscrypt_auth will need to be freed in
> ceph_mdsc_release_request().  (I believe you've moved this function to
> some other commit in your experimental branch).
> 

Ahh yes. Good catch. I'll fix that up too.

> > diff --git a/fs/ceph/crypto.h b/fs/ceph/crypto.h
> > index d2b1f8e7b300..bdf1ba47db16 100644
> > --- a/fs/ceph/crypto.h
> > +++ b/fs/ceph/crypto.h
> > @@ -11,6 +11,9 @@
> >  #define	CEPH_XATTR_NAME_ENCRYPTION_CONTEXT	"encryption.ctx"
> >  
> >  #ifdef CONFIG_FS_ENCRYPTION
> > +struct ceph_fs_client;
> > +struct ceph_acl_sec_ctx;
> > +struct ceph_mds_request;
> >  
> >  #define CEPH_FSCRYPT_AUTH_VERSION	1
> >  struct ceph_fscrypt_auth {
> > @@ -19,10 +22,19 @@ struct ceph_fscrypt_auth {
> >  	u8	cfa_blob[FSCRYPT_SET_CONTEXT_MAX_SIZE];
> >  } __packed;
> >  
> > +static inline u32 ceph_fscrypt_auth_size(u32 ctxsize)
> > +{
> > +	return offsetof(struct ceph_fscrypt_auth, cfa_blob) + ctxsize;
> > +}
> > +
> >  void ceph_fscrypt_set_ops(struct super_block *sb);
> >  
> >  void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc);
> >  
> > +int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
> > +				 struct ceph_acl_sec_ctx *as);
> > +void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req, struct ceph_acl_sec_ctx *as);
> > +
> >  #else /* CONFIG_FS_ENCRYPTION */
> >  
> >  static inline void ceph_fscrypt_set_ops(struct super_block *sb)
> > @@ -32,6 +44,19 @@ static inline void ceph_fscrypt_set_ops(struct super_block *sb)
> >  static inline void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc)
> >  {
> >  }
> > +
> > +static inline int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
> > +						struct ceph_acl_sec_ctx *as)
> > +{
> > +	if (IS_ENCRYPTED(dir))
> > +		return -EOPNOTSUPP;
> > +	return 0;
> > +}
> > +
> > +static inline void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
> > +						struct ceph_acl_sec_ctx *as_ctx)
> > +{
> > +}
> >  #endif /* CONFIG_FS_ENCRYPTION */
> >  
> >  #endif
> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > index fba139a4f57b..a0b311195e80 100644
> > --- a/fs/ceph/inode.c
> > +++ b/fs/ceph/inode.c
> > @@ -83,12 +83,17 @@ struct inode *ceph_new_inode(struct inode *dir, struct dentry *dentry,
> >  			goto out_err;
> >  	}
> >  
> > +	inode->i_state = 0;
> > +	inode->i_mode = *mode;
> > +
> >  	err = ceph_security_init_secctx(dentry, *mode, as_ctx);
> >  	if (err < 0)
> >  		goto out_err;
> >  
> > -	inode->i_state = 0;
> > -	inode->i_mode = *mode;
> > +	err = ceph_fscrypt_prepare_context(dir, inode, as_ctx);
> > +	if (err)
> > +		goto out_err;
> > +
> >  	return inode;
> >  out_err:
> >  	iput(inode);
> > @@ -101,6 +106,7 @@ void ceph_as_ctx_to_req(struct ceph_mds_request *req, struct ceph_acl_sec_ctx *a
> >  		req->r_pagelist = as_ctx->pagelist;
> >  		as_ctx->pagelist = NULL;
> >  	}
> > +	ceph_fscrypt_as_ctx_to_req(req, as_ctx);
> >  }
> >  
> >  /**
> > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > index 534c2a76562d..651d7909a443 100644
> > --- a/fs/ceph/super.h
> > +++ b/fs/ceph/super.h
> > @@ -26,6 +26,8 @@
> >  #include <linux/fscache.h>
> >  #endif
> > 
> > +#include "crypto.h"
> > +
> >  /* f_type in struct statfs */
> >  #define CEPH_SUPER_MAGIC 0x00c36400
> >  
> > @@ -1068,6 +1070,9 @@ struct ceph_acl_sec_ctx {
> >  #ifdef CONFIG_CEPH_FS_SECURITY_LABEL
> >  	void *sec_ctx;
> >  	u32 sec_ctxlen;
> > +#endif
> > +#ifdef CONFIG_FS_ENCRYPTION
> > +	struct ceph_fscrypt_auth *fscrypt_auth;
> >  #endif
> >  	struct ceph_pagelist *pagelist;
> >  };
> > diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
> > index 1242db8d3444..16a62a2bd61e 100644
> > --- a/fs/ceph/xattr.c
> > +++ b/fs/ceph/xattr.c
> > @@ -1362,6 +1362,9 @@ void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx)
> >  #endif
> >  #ifdef CONFIG_CEPH_FS_SECURITY_LABEL
> >  	security_release_secctx(as_ctx->sec_ctx, as_ctx->sec_ctxlen);
> > +#endif
> > +#ifdef CONFIG_FS_ENCRYPTION
> > +	kfree(as_ctx->fscrypt_auth);
> >  #endif
> >  	if (as_ctx->pagelist)
> >  		ceph_pagelist_release(as_ctx->pagelist);
> > -- 
> > 2.31.1
> > 

-- 
Jeff Layton <jlayton@kernel.org>