[v2] ceph: don't allow access to MDS-private inodes

Commit Message

Jeff Layton April 20, 2021, 2:06 p.m. UTC

The MDS reserves a set of inodes for its own usage, and these should
never be accessible to clients. Add a new helper to vet a proposed
inode number against that range, and complain loudly and refuse to
create or look it up if it's in it. We do need to carve out an exception
for the root and the lost+found directories.

Also, ensure that the MDS doesn't try to delegate that range to us
either. Print a warning if it does, and don't save the range in the
xarray.

URL: https://tracker.ceph.com/issues/49922
Signed-off-by: Jeff Layton <[e-mail]>
Signed-off-by: Xiubo Li<[e-mail]>
Reviewed-by: Patrick Donnelly <[e-mail]>
---
 fs/ceph/export.c             |  8 ++++++++
 fs/ceph/inode.c              |  3 +++
 fs/ceph/mds_client.c         |  7 +++++++
 fs/ceph/super.h              | 24 ++++++++++++++++++++++++
 include/linux/ceph/ceph_fs.h |  7 ++++---
 5 files changed, 46 insertions(+), 3 deletions(-)

v2: allow lookups of lost+found dir inodes
    flesh out and update the CEPH_INO_* definitions

Comments

Xiubo Li April 21, 2021, 12:05 a.m. UTC | #1

On 2021/4/20 22:06, Jeff Layton wrote:
> The MDS reserves a set of inodes for its own usage, and these should
> never be accessible to clients. Add a new helper to vet a proposed
> inode number against that range, and complain loudly and refuse to
> create or look it up if it's in it. We do need to carve out an exception
> for the root and the lost+found directories.
>
> Also, ensure that the MDS doesn't try to delegate that range to us
> either. Print a warning if it does, and don't save the range in the
> xarray.
>
> URL: https://tracker.ceph.com/issues/49922
> Signed-off-by: Jeff Layton <[e-mail]>
> Signed-off-by: Xiubo Li<[e-mail]>
> Reviewed-by: Patrick Donnelly <[e-mail]>
> ---
>   fs/ceph/export.c             |  8 ++++++++
>   fs/ceph/inode.c              |  3 +++
>   fs/ceph/mds_client.c         |  7 +++++++
>   fs/ceph/super.h              | 24 ++++++++++++++++++++++++
>   include/linux/ceph/ceph_fs.h |  7 ++++---
>   5 files changed, 46 insertions(+), 3 deletions(-)
>
> v2: allow lookups of lost+found dir inodes
>      flesh out and update the CEPH_INO_* definitions
>
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 17d8c8f4ec89..65540a4429b2 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
>   
>   	vino.ino = ino;
>   	vino.snap = CEPH_NOSNAP;
> +
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-ESTALE);
> +
>   	inode = ceph_find_inode(sb, vino);
>   	if (!inode) {
>   		struct ceph_mds_request *req;
> @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
>   		vino.ino = sfh->ino;
>   		vino.snap = sfh->snapid;
>   	}
> +
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-ESTALE);
> +
>   	inode = ceph_find_inode(sb, vino);
>   	if (inode)
>   		return d_obtain_alias(inode);
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 14a1f7963625..e1c63adb196d 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
>   {
>   	struct inode *inode;
>   
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-EREMOTEIO);
> +
>   	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
>   			     ceph_set_ino_cb, &vino);
>   	if (!inode)
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index 63b53098360c..e5af591d3bd4 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
>   
>   		ceph_decode_64_safe(p, end, start, bad);
>   		ceph_decode_64_safe(p, end, len, bad);
> +
> +		/* Don't accept a delegation of system inodes */
> +		if (start < CEPH_INO_SYSTEM_BASE) {
> +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
> +					start, len);
> +			continue;
> +		}
>   		while (len--) {
>   			int err = xa_insert(&s->s_delegated_inos, ino = start++,
>   					    DELEGATED_INO_AVAILABLE,
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index df0851b9240e..f1745403c9b0 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
>   		ci->i_vino.snap == pvino->snap;
>   }
>   
> +/*
> + * The MDS reserves a set of inodes for its own usage. These should never
> + * be accessible by clients, and so the MDS has no reason to ever hand these
> + * out.
> + *
> + * These come from src/mds/mdstypes.h in the ceph sources.
> + */
> +#define CEPH_MAX_MDS		0x100
> +#define CEPH_NUM_STRAY		10
> +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
> +
> +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
> +{
> +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
> +	    vino.ino != CEPH_INO_ROOT &&
> +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
> +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
> +		return true;
> +	}
> +	return false;
> +}
>   
>   static inline struct inode *ceph_find_inode(struct super_block *sb,
>   					    struct ceph_vino vino)
>   {
> +	if (ceph_vino_is_reserved(vino))
> +		return NULL;
> +
>   	/*
>   	 * NB: The hashval will be run through the fs/inode.c hash function
>   	 * anyway, so there is no need to squash the inode number down to
> diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
> index e41a811026f6..3c90ae21a7e1 100644
> --- a/include/linux/ceph/ceph_fs.h
> +++ b/include/linux/ceph/ceph_fs.h
> @@ -27,9 +27,10 @@
>   #define CEPH_MONC_PROTOCOL   15 /* server/client */
>   
>   
> -#define CEPH_INO_ROOT   1
> -#define CEPH_INO_CEPH   2       /* hidden .ceph dir */
> -#define CEPH_INO_DOTDOT 3	/* used by ceph fuse for parent (..) */
> +#define CEPH_INO_ROOT			1 /* root inode number for all cephfs's */
> +#define CEPH_INO_CEPH			2 /* hidden .ceph dir */
> +#define CEPH_INO_GLOBAL_SNAPREALM	3 /* includes all snapshots in the fs */
> +#define CEPH_INO_LOST_AND_FOUND		4 /* lost+found dir */
>   
>   /* arbitrary limit on max # of monitors (cluster of 3 is typical) */
>   #define CEPH_MAX_MON   31

LTGM. Thanks.

Luis Henriques April 21, 2021, 4:22 p.m. UTC | #2

Jeff Layton <[e-mail]> writes:

> The MDS reserves a set of inodes for its own usage, and these should
> never be accessible to clients. Add a new helper to vet a proposed
> inode number against that range, and complain loudly and refuse to
> create or look it up if it's in it. We do need to carve out an exception
> for the root and the lost+found directories.
>
> Also, ensure that the MDS doesn't try to delegate that range to us
> either. Print a warning if it does, and don't save the range in the
> xarray.
>
> URL: https://tracker.ceph.com/issues/49922
> Signed-off-by: Jeff Layton <[e-mail]>
> Signed-off-by: Xiubo Li<[e-mail]>
> Reviewed-by: Patrick Donnelly <[e-mail]>
> ---
>  fs/ceph/export.c             |  8 ++++++++
>  fs/ceph/inode.c              |  3 +++
>  fs/ceph/mds_client.c         |  7 +++++++
>  fs/ceph/super.h              | 24 ++++++++++++++++++++++++
>  include/linux/ceph/ceph_fs.h |  7 ++++---
>  5 files changed, 46 insertions(+), 3 deletions(-)
>
> v2: allow lookups of lost+found dir inodes
>     flesh out and update the CEPH_INO_* definitions
>
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 17d8c8f4ec89..65540a4429b2 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
>  
>  	vino.ino = ino;
>  	vino.snap = CEPH_NOSNAP;
> +
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-ESTALE);
> +
>  	inode = ceph_find_inode(sb, vino);
>  	if (!inode) {
>  		struct ceph_mds_request *req;
> @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
>  		vino.ino = sfh->ino;
>  		vino.snap = sfh->snapid;
>  	}
> +
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-ESTALE);
> +
>  	inode = ceph_find_inode(sb, vino);
>  	if (inode)
>  		return d_obtain_alias(inode);
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 14a1f7963625..e1c63adb196d 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
>  {
>  	struct inode *inode;
>  
> +	if (ceph_vino_is_reserved(vino))
> +		return ERR_PTR(-EREMOTEIO);
> +
>  	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
>  			     ceph_set_ino_cb, &vino);
>  	if (!inode)
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index 63b53098360c..e5af591d3bd4 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
>  
>  		ceph_decode_64_safe(p, end, start, bad);
>  		ceph_decode_64_safe(p, end, len, bad);
> +
> +		/* Don't accept a delegation of system inodes */
> +		if (start < CEPH_INO_SYSTEM_BASE) {
> +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
> +					start, len);
> +			continue;
> +		}
>  		while (len--) {
>  			int err = xa_insert(&s->s_delegated_inos, ino = start++,
>  					    DELEGATED_INO_AVAILABLE,
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index df0851b9240e..f1745403c9b0 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
>  		ci->i_vino.snap == pvino->snap;
>  }
>  
> +/*
> + * The MDS reserves a set of inodes for its own usage. These should never
> + * be accessible by clients, and so the MDS has no reason to ever hand these
> + * out.
> + *
> + * These come from src/mds/mdstypes.h in the ceph sources.
> + */
> +#define CEPH_MAX_MDS		0x100
> +#define CEPH_NUM_STRAY		10
> +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
> +
> +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
> +{
> +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
> +	    vino.ino != CEPH_INO_ROOT &&
> +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
> +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);

This warning is quite easy to hit with inode 0x3, using generic/013.  It
looks like, while looking for the snaprealm to check quotas, we will
eventually get this value from the MDS.  So this function should also
return 'true' if ino is CEPH_INO_GLOBAL_SNAPREALM.

Cheers,

Jeff Layton April 21, 2021, 4:48 p.m. UTC | #3

On Wed, 2021-04-21 at 17:22 +0100, Luis Henriques wrote:
> Jeff Layton <[e-mail]> writes:
> 
> > The MDS reserves a set of inodes for its own usage, and these should
> > never be accessible to clients. Add a new helper to vet a proposed
> > inode number against that range, and complain loudly and refuse to
> > create or look it up if it's in it. We do need to carve out an exception
> > for the root and the lost+found directories.
> > 
> > Also, ensure that the MDS doesn't try to delegate that range to us
> > either. Print a warning if it does, and don't save the range in the
> > xarray.
> > 
> > URL: https://tracker.ceph.com/issues/49922
> > Signed-off-by: Jeff Layton <[e-mail]>
> > Signed-off-by: Xiubo Li<[e-mail]>
> > Reviewed-by: Patrick Donnelly <[e-mail]>
> > ---
> >  fs/ceph/export.c             |  8 ++++++++
> >  fs/ceph/inode.c              |  3 +++
> >  fs/ceph/mds_client.c         |  7 +++++++
> >  fs/ceph/super.h              | 24 ++++++++++++++++++++++++
> >  include/linux/ceph/ceph_fs.h |  7 ++++---
> >  5 files changed, 46 insertions(+), 3 deletions(-)
> > 
> > v2: allow lookups of lost+found dir inodes
> >     flesh out and update the CEPH_INO_* definitions
> > 
> > diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> > index 17d8c8f4ec89..65540a4429b2 100644
> > --- a/fs/ceph/export.c
> > +++ b/fs/ceph/export.c
> > @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
> >  
> >  	vino.ino = ino;
> >  	vino.snap = CEPH_NOSNAP;
> > +
> > +	if (ceph_vino_is_reserved(vino))
> > +		return ERR_PTR(-ESTALE);
> > +
> >  	inode = ceph_find_inode(sb, vino);
> >  	if (!inode) {
> >  		struct ceph_mds_request *req;
> > @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
> >  		vino.ino = sfh->ino;
> >  		vino.snap = sfh->snapid;
> >  	}
> > +
> > +	if (ceph_vino_is_reserved(vino))
> > +		return ERR_PTR(-ESTALE);
> > +
> >  	inode = ceph_find_inode(sb, vino);
> >  	if (inode)
> >  		return d_obtain_alias(inode);
> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > index 14a1f7963625..e1c63adb196d 100644
> > --- a/fs/ceph/inode.c
> > +++ b/fs/ceph/inode.c
> > @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
> >  {
> >  	struct inode *inode;
> >  
> > +	if (ceph_vino_is_reserved(vino))
> > +		return ERR_PTR(-EREMOTEIO);
> > +
> >  	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
> >  			     ceph_set_ino_cb, &vino);
> >  	if (!inode)
> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > index 63b53098360c..e5af591d3bd4 100644
> > --- a/fs/ceph/mds_client.c
> > +++ b/fs/ceph/mds_client.c
> > @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
> >  
> >  		ceph_decode_64_safe(p, end, start, bad);
> >  		ceph_decode_64_safe(p, end, len, bad);
> > +
> > +		/* Don't accept a delegation of system inodes */
> > +		if (start < CEPH_INO_SYSTEM_BASE) {
> > +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
> > +					start, len);
> > +			continue;
> > +		}
> >  		while (len--) {
> >  			int err = xa_insert(&s->s_delegated_inos, ino = start++,
> >  					    DELEGATED_INO_AVAILABLE,
> > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > index df0851b9240e..f1745403c9b0 100644
> > --- a/fs/ceph/super.h
> > +++ b/fs/ceph/super.h
> > @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
> >  		ci->i_vino.snap == pvino->snap;
> >  }
> >  
> > +/*
> > + * The MDS reserves a set of inodes for its own usage. These should never
> > + * be accessible by clients, and so the MDS has no reason to ever hand these
> > + * out.
> > + *
> > + * These come from src/mds/mdstypes.h in the ceph sources.
> > + */
> > +#define CEPH_MAX_MDS		0x100
> > +#define CEPH_NUM_STRAY		10
> > +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
> > +
> > +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
> > +{
> > +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
> > +	    vino.ino != CEPH_INO_ROOT &&
> > +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
> > +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
> 
> This warning is quite easy to hit with inode 0x3, using generic/013.  It
> looks like, while looking for the snaprealm to check quotas, we will
> eventually get this value from the MDS.  So this function should also
> return 'true' if ino is CEPH_INO_GLOBAL_SNAPREALM.
> 

I wonder why I'm not seeing this. What mount options are you using?

Thanks,

Luis Henriques April 21, 2021, 5:46 p.m. UTC | #4

Jeff Layton <[e-mail]> writes:

> On Wed, 2021-04-21 at 17:22 +0100, Luis Henriques wrote:
>> Jeff Layton <[e-mail]> writes:
>> 
>> > The MDS reserves a set of inodes for its own usage, and these should
>> > never be accessible to clients. Add a new helper to vet a proposed
>> > inode number against that range, and complain loudly and refuse to
>> > create or look it up if it's in it. We do need to carve out an exception
>> > for the root and the lost+found directories.
>> > 
>> > Also, ensure that the MDS doesn't try to delegate that range to us
>> > either. Print a warning if it does, and don't save the range in the
>> > xarray.
>> > 
>> > URL: https://tracker.ceph.com/issues/49922
>> > Signed-off-by: Jeff Layton <[e-mail]>
>> > Signed-off-by: Xiubo Li<[e-mail]>
>> > Reviewed-by: Patrick Donnelly <[e-mail]>
>> > ---
>> >  fs/ceph/export.c             |  8 ++++++++
>> >  fs/ceph/inode.c              |  3 +++
>> >  fs/ceph/mds_client.c         |  7 +++++++
>> >  fs/ceph/super.h              | 24 ++++++++++++++++++++++++
>> >  include/linux/ceph/ceph_fs.h |  7 ++++---
>> >  5 files changed, 46 insertions(+), 3 deletions(-)
>> > 
>> > v2: allow lookups of lost+found dir inodes
>> >     flesh out and update the CEPH_INO_* definitions
>> > 
>> > diff --git a/fs/ceph/export.c b/fs/ceph/export.c
>> > index 17d8c8f4ec89..65540a4429b2 100644
>> > --- a/fs/ceph/export.c
>> > +++ b/fs/ceph/export.c
>> > @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
>> >  
>> >  	vino.ino = ino;
>> >  	vino.snap = CEPH_NOSNAP;
>> > +
>> > +	if (ceph_vino_is_reserved(vino))
>> > +		return ERR_PTR(-ESTALE);
>> > +
>> >  	inode = ceph_find_inode(sb, vino);
>> >  	if (!inode) {
>> >  		struct ceph_mds_request *req;
>> > @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
>> >  		vino.ino = sfh->ino;
>> >  		vino.snap = sfh->snapid;
>> >  	}
>> > +
>> > +	if (ceph_vino_is_reserved(vino))
>> > +		return ERR_PTR(-ESTALE);
>> > +
>> >  	inode = ceph_find_inode(sb, vino);
>> >  	if (inode)
>> >  		return d_obtain_alias(inode);
>> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
>> > index 14a1f7963625..e1c63adb196d 100644
>> > --- a/fs/ceph/inode.c
>> > +++ b/fs/ceph/inode.c
>> > @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
>> >  {
>> >  	struct inode *inode;
>> >  
>> > +	if (ceph_vino_is_reserved(vino))
>> > +		return ERR_PTR(-EREMOTEIO);
>> > +
>> >  	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
>> >  			     ceph_set_ino_cb, &vino);
>> >  	if (!inode)
>> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>> > index 63b53098360c..e5af591d3bd4 100644
>> > --- a/fs/ceph/mds_client.c
>> > +++ b/fs/ceph/mds_client.c
>> > @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
>> >  
>> >  		ceph_decode_64_safe(p, end, start, bad);
>> >  		ceph_decode_64_safe(p, end, len, bad);
>> > +
>> > +		/* Don't accept a delegation of system inodes */
>> > +		if (start < CEPH_INO_SYSTEM_BASE) {
>> > +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
>> > +					start, len);
>> > +			continue;
>> > +		}
>> >  		while (len--) {
>> >  			int err = xa_insert(&s->s_delegated_inos, ino = start++,
>> >  					    DELEGATED_INO_AVAILABLE,
>> > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>> > index df0851b9240e..f1745403c9b0 100644
>> > --- a/fs/ceph/super.h
>> > +++ b/fs/ceph/super.h
>> > @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
>> >  		ci->i_vino.snap == pvino->snap;
>> >  }
>> >  
>> > +/*
>> > + * The MDS reserves a set of inodes for its own usage. These should never
>> > + * be accessible by clients, and so the MDS has no reason to ever hand these
>> > + * out.
>> > + *
>> > + * These come from src/mds/mdstypes.h in the ceph sources.
>> > + */
>> > +#define CEPH_MAX_MDS		0x100
>> > +#define CEPH_NUM_STRAY		10
>> > +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
>> > +
>> > +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
>> > +{
>> > +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
>> > +	    vino.ino != CEPH_INO_ROOT &&
>> > +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
>> > +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
>> 
>> This warning is quite easy to hit with inode 0x3, using generic/013.  It
>> looks like, while looking for the snaprealm to check quotas, we will
>> eventually get this value from the MDS.  So this function should also
>> return 'true' if ino is CEPH_INO_GLOBAL_SNAPREALM.
>> 
>
> I wonder why I'm not seeing this. What mount options are you using?

Ah, I should have mentioned that.  I'm seeing this when using 'copyfrom'
mount option, but (and more important!) I'm also not mounting the
filesystem on the "real" root, i.e. I'm doing something like:

 mount -t ceph <ip>:<port>:/test /mnt/ ...

Not mounting on the FS root will allow us to get function
ceph_has_realms_with_quotas() to return 'true'.

For reference, I'm including the WARNING bellow.

Cheers,

Jeff Layton April 21, 2021, 6:18 p.m. UTC | #5

On Wed, 2021-04-21 at 18:46 +0100, Luis Henriques wrote:
> Jeff Layton <[e-mail]> writes:
> 
> > On Wed, 2021-04-21 at 17:22 +0100, Luis Henriques wrote:
> > > Jeff Layton <[e-mail]> writes:
> > > 
> > > > The MDS reserves a set of inodes for its own usage, and these should
> > > > never be accessible to clients. Add a new helper to vet a proposed
> > > > inode number against that range, and complain loudly and refuse to
> > > > create or look it up if it's in it. We do need to carve out an exception
> > > > for the root and the lost+found directories.
> > > > 
> > > > Also, ensure that the MDS doesn't try to delegate that range to us
> > > > either. Print a warning if it does, and don't save the range in the
> > > > xarray.
> > > > 
> > > > URL: https://tracker.ceph.com/issues/49922
> > > > Signed-off-by: Jeff Layton <[e-mail]>
> > > > Signed-off-by: Xiubo Li<[e-mail]>
> > > > Reviewed-by: Patrick Donnelly <[e-mail]>
> > > > ---
> > > >  fs/ceph/export.c             |  8 ++++++++
> > > >  fs/ceph/inode.c              |  3 +++
> > > >  fs/ceph/mds_client.c         |  7 +++++++
> > > >  fs/ceph/super.h              | 24 ++++++++++++++++++++++++
> > > >  include/linux/ceph/ceph_fs.h |  7 ++++---
> > > >  5 files changed, 46 insertions(+), 3 deletions(-)
> > > > 
> > > > v2: allow lookups of lost+found dir inodes
> > > >     flesh out and update the CEPH_INO_* definitions
> > > > 
> > > > diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> > > > index 17d8c8f4ec89..65540a4429b2 100644
> > > > --- a/fs/ceph/export.c
> > > > +++ b/fs/ceph/export.c
> > > > @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
> > > >  
> > > > 
> > > > 
> > > > 
> > > >  	vino.ino = ino;
> > > >  	vino.snap = CEPH_NOSNAP;
> > > > +
> > > > +	if (ceph_vino_is_reserved(vino))
> > > > +		return ERR_PTR(-ESTALE);
> > > > +
> > > >  	inode = ceph_find_inode(sb, vino);
> > > >  	if (!inode) {
> > > >  		struct ceph_mds_request *req;
> > > > @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
> > > >  		vino.ino = sfh->ino;
> > > >  		vino.snap = sfh->snapid;
> > > >  	}
> > > > +
> > > > +	if (ceph_vino_is_reserved(vino))
> > > > +		return ERR_PTR(-ESTALE);
> > > > +
> > > >  	inode = ceph_find_inode(sb, vino);
> > > >  	if (inode)
> > > >  		return d_obtain_alias(inode);
> > > > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > > > index 14a1f7963625..e1c63adb196d 100644
> > > > --- a/fs/ceph/inode.c
> > > > +++ b/fs/ceph/inode.c
> > > > @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
> > > >  {
> > > >  	struct inode *inode;
> > > >  
> > > > 
> > > > 
> > > > 
> > > > +	if (ceph_vino_is_reserved(vino))
> > > > +		return ERR_PTR(-EREMOTEIO);
> > > > +
> > > >  	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
> > > >  			     ceph_set_ino_cb, &vino);
> > > >  	if (!inode)
> > > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > > > index 63b53098360c..e5af591d3bd4 100644
> > > > --- a/fs/ceph/mds_client.c
> > > > +++ b/fs/ceph/mds_client.c
> > > > @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
> > > >  
> > > > 
> > > > 
> > > > 
> > > >  		ceph_decode_64_safe(p, end, start, bad);
> > > >  		ceph_decode_64_safe(p, end, len, bad);
> > > > +
> > > > +		/* Don't accept a delegation of system inodes */
> > > > +		if (start < CEPH_INO_SYSTEM_BASE) {
> > > > +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
> > > > +					start, len);
> > > > +			continue;
> > > > +		}
> > > >  		while (len--) {
> > > >  			int err = xa_insert(&s->s_delegated_inos, ino = start++,
> > > >  					    DELEGATED_INO_AVAILABLE,
> > > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > > > index df0851b9240e..f1745403c9b0 100644
> > > > --- a/fs/ceph/super.h
> > > > +++ b/fs/ceph/super.h
> > > > @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
> > > >  		ci->i_vino.snap == pvino->snap;
> > > >  }
> > > >  
> > > > 
> > > > 
> > > > 
> > > > +/*
> > > > + * The MDS reserves a set of inodes for its own usage. These should never
> > > > + * be accessible by clients, and so the MDS has no reason to ever hand these
> > > > + * out.
> > > > + *
> > > > + * These come from src/mds/mdstypes.h in the ceph sources.
> > > > + */
> > > > +#define CEPH_MAX_MDS		0x100
> > > > +#define CEPH_NUM_STRAY		10
> > > > +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
> > > > +
> > > > +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
> > > > +{
> > > > +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
> > > > +	    vino.ino != CEPH_INO_ROOT &&
> > > > +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
> > > > +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
> > > 
> > > This warning is quite easy to hit with inode 0x3, using generic/013.  It
> > > looks like, while looking for the snaprealm to check quotas, we will
> > > eventually get this value from the MDS.  So this function should also
> > > return 'true' if ino is CEPH_INO_GLOBAL_SNAPREALM.
> > > 
> > 
> > I wonder why I'm not seeing this. What mount options are you using?
> 
> Ah, I should have mentioned that.  I'm seeing this when using 'copyfrom'
> mount option, but (and more important!) I'm also not mounting the
> filesystem on the "real" root, i.e. I'm doing something like:
> 
>  mount -t ceph <ip>:<port>:/test /mnt/ ...
> 
> Not mounting on the FS root will allow us to get function
> ceph_has_realms_with_quotas() to return 'true'.
> 
> For reference, I'm including the WARNING bellow.
> 
> Cheers,

Thanks, that makes sense. At this point, I think we ought to probably
just assume that the very low inode numbers (0..0xff) are eligible to
be looked up by the MDS.

I'll send a v3 patch in a bit with what I think we might want.

Xiubo Li April 22, 2021, 1:48 a.m. UTC | #6

On 2021/4/22 1:46, Luis Henriques wrote:
> Jeff Layton <[e-mail]> writes:
>
>> On Wed, 2021-04-21 at 17:22 +0100, Luis Henriques wrote:
>>> Jeff Layton <[e-mail]> writes:
>>>
>>>> The MDS reserves a set of inodes for its own usage, and these should
>>>> never be accessible to clients. Add a new helper to vet a proposed
>>>> inode number against that range, and complain loudly and refuse to
>>>> create or look it up if it's in it. We do need to carve out an exception
>>>> for the root and the lost+found directories.
>>>>
>>>> Also, ensure that the MDS doesn't try to delegate that range to us
>>>> either. Print a warning if it does, and don't save the range in the
>>>> xarray.
>>>>
>>>> URL: https://tracker.ceph.com/issues/49922
>>>> Signed-off-by: Jeff Layton <[e-mail]>
>>>> Signed-off-by: Xiubo Li<[e-mail]>
>>>> Reviewed-by: Patrick Donnelly <[e-mail]>
>>>> ---
>>>>   fs/ceph/export.c             |  8 ++++++++
>>>>   fs/ceph/inode.c              |  3 +++
>>>>   fs/ceph/mds_client.c         |  7 +++++++
>>>>   fs/ceph/super.h              | 24 ++++++++++++++++++++++++
>>>>   include/linux/ceph/ceph_fs.h |  7 ++++---
>>>>   5 files changed, 46 insertions(+), 3 deletions(-)
>>>>
>>>> v2: allow lookups of lost+found dir inodes
>>>>      flesh out and update the CEPH_INO_* definitions
>>>>
>>>> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
>>>> index 17d8c8f4ec89..65540a4429b2 100644
>>>> --- a/fs/ceph/export.c
>>>> +++ b/fs/ceph/export.c
>>>> @@ -129,6 +129,10 @@ static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
>>>>   
>>>>   	vino.ino = ino;
>>>>   	vino.snap = CEPH_NOSNAP;
>>>> +
>>>> +	if (ceph_vino_is_reserved(vino))
>>>> +		return ERR_PTR(-ESTALE);
>>>> +
>>>>   	inode = ceph_find_inode(sb, vino);
>>>>   	if (!inode) {
>>>>   		struct ceph_mds_request *req;
>>>> @@ -214,6 +218,10 @@ static struct dentry *__snapfh_to_dentry(struct super_block *sb,
>>>>   		vino.ino = sfh->ino;
>>>>   		vino.snap = sfh->snapid;
>>>>   	}
>>>> +
>>>> +	if (ceph_vino_is_reserved(vino))
>>>> +		return ERR_PTR(-ESTALE);
>>>> +
>>>>   	inode = ceph_find_inode(sb, vino);
>>>>   	if (inode)
>>>>   		return d_obtain_alias(inode);
>>>> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
>>>> index 14a1f7963625..e1c63adb196d 100644
>>>> --- a/fs/ceph/inode.c
>>>> +++ b/fs/ceph/inode.c
>>>> @@ -56,6 +56,9 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
>>>>   {
>>>>   	struct inode *inode;
>>>>   
>>>> +	if (ceph_vino_is_reserved(vino))
>>>> +		return ERR_PTR(-EREMOTEIO);
>>>> +
>>>>   	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
>>>>   			     ceph_set_ino_cb, &vino);
>>>>   	if (!inode)
>>>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>>>> index 63b53098360c..e5af591d3bd4 100644
>>>> --- a/fs/ceph/mds_client.c
>>>> +++ b/fs/ceph/mds_client.c
>>>> @@ -440,6 +440,13 @@ static int ceph_parse_deleg_inos(void **p, void *end,
>>>>   
>>>>   		ceph_decode_64_safe(p, end, start, bad);
>>>>   		ceph_decode_64_safe(p, end, len, bad);
>>>> +
>>>> +		/* Don't accept a delegation of system inodes */
>>>> +		if (start < CEPH_INO_SYSTEM_BASE) {
>>>> +			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
>>>> +					start, len);
>>>> +			continue;
>>>> +		}
>>>>   		while (len--) {
>>>>   			int err = xa_insert(&s->s_delegated_inos, ino = start++,
>>>>   					    DELEGATED_INO_AVAILABLE,
>>>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>>>> index df0851b9240e..f1745403c9b0 100644
>>>> --- a/fs/ceph/super.h
>>>> +++ b/fs/ceph/super.h
>>>> @@ -529,10 +529,34 @@ static inline int ceph_ino_compare(struct inode *inode, void *data)
>>>>   		ci->i_vino.snap == pvino->snap;
>>>>   }
>>>>   
>>>> +/*
>>>> + * The MDS reserves a set of inodes for its own usage. These should never
>>>> + * be accessible by clients, and so the MDS has no reason to ever hand these
>>>> + * out.
>>>> + *
>>>> + * These come from src/mds/mdstypes.h in the ceph sources.
>>>> + */
>>>> +#define CEPH_MAX_MDS		0x100
>>>> +#define CEPH_NUM_STRAY		10
>>>> +#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
>>>> +
>>>> +static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
>>>> +{
>>>> +	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
>>>> +	    vino.ino != CEPH_INO_ROOT &&
>>>> +	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
>>>> +		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
>>> This warning is quite easy to hit with inode 0x3, using generic/013.  It
>>> looks like, while looking for the snaprealm to check quotas, we will
>>> eventually get this value from the MDS.  So this function should also
>>> return 'true' if ino is CEPH_INO_GLOBAL_SNAPREALM.
>>>
>> I wonder why I'm not seeing this. What mount options are you using?
> Ah, I should have mentioned that.  I'm seeing this when using 'copyfrom'
> mount option, but (and more important!) I'm also not mounting the
> filesystem on the "real" root, i.e. I'm doing something like:
>
>   mount -t ceph <ip>:<port>:/test /mnt/ ...
>
> Not mounting on the FS root will allow us to get function
> ceph_has_realms_with_quotas() to return 'true'.
>
> For reference, I'm including the WARNING bellow.

Good catch Luis.

Yeah, when lookup the global snaprealm ino, it will hit this. I will 
update my PR in libcephfs.

Thanks

BRs


> Cheers,

Patch

diff --git a/fs/ceph/export.c b/fs/ceph/export.c
index 17d8c8f4ec89..65540a4429b2 100644
--- a/fs/ceph/export.c
+++ b/fs/ceph/export.c
@@ -129,6 +129,10 @@  static struct inode *__lookup_inode(struct super_block *sb, u64 ino)
 
 	vino.ino = ino;
 	vino.snap = CEPH_NOSNAP;
+
+	if (ceph_vino_is_reserved(vino))
+		return ERR_PTR(-ESTALE);
+
 	inode = ceph_find_inode(sb, vino);
 	if (!inode) {
 		struct ceph_mds_request *req;
@@ -214,6 +218,10 @@  static struct dentry *__snapfh_to_dentry(struct super_block *sb,
 		vino.ino = sfh->ino;
 		vino.snap = sfh->snapid;
 	}
+
+	if (ceph_vino_is_reserved(vino))
+		return ERR_PTR(-ESTALE);
+
 	inode = ceph_find_inode(sb, vino);
 	if (inode)
 		return d_obtain_alias(inode);
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 14a1f7963625..e1c63adb196d 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -56,6 +56,9 @@  struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
 {
 	struct inode *inode;
 
+	if (ceph_vino_is_reserved(vino))
+		return ERR_PTR(-EREMOTEIO);
+
 	inode = iget5_locked(sb, (unsigned long)vino.ino, ceph_ino_compare,
 			     ceph_set_ino_cb, &vino);
 	if (!inode)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 63b53098360c..e5af591d3bd4 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -440,6 +440,13 @@  static int ceph_parse_deleg_inos(void **p, void *end,
 
 		ceph_decode_64_safe(p, end, start, bad);
 		ceph_decode_64_safe(p, end, len, bad);
+
+		/* Don't accept a delegation of system inodes */
+		if (start < CEPH_INO_SYSTEM_BASE) {
+			pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
+					start, len);
+			continue;
+		}
 		while (len--) {
 			int err = xa_insert(&s->s_delegated_inos, ino = start++,
 					    DELEGATED_INO_AVAILABLE,
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index df0851b9240e..f1745403c9b0 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -529,10 +529,34 @@  static inline int ceph_ino_compare(struct inode *inode, void *data)
 		ci->i_vino.snap == pvino->snap;
 }
 
+/*
+ * The MDS reserves a set of inodes for its own usage. These should never
+ * be accessible by clients, and so the MDS has no reason to ever hand these
+ * out.
+ *
+ * These come from src/mds/mdstypes.h in the ceph sources.
+ */
+#define CEPH_MAX_MDS		0x100
+#define CEPH_NUM_STRAY		10
+#define CEPH_INO_SYSTEM_BASE	((6*CEPH_MAX_MDS) + (CEPH_MAX_MDS * CEPH_NUM_STRAY))
+
+static inline bool ceph_vino_is_reserved(const struct ceph_vino vino)
+{
+	if (vino.ino < CEPH_INO_SYSTEM_BASE &&
+	    vino.ino != CEPH_INO_ROOT &&
+	    vino.ino != CEPH_INO_LOST_AND_FOUND) {
+		WARN_RATELIMIT(1, "Attempt to access reserved inode number 0x%llx", vino.ino);
+		return true;
+	}
+	return false;
+}
 
 static inline struct inode *ceph_find_inode(struct super_block *sb,
 					    struct ceph_vino vino)
 {
+	if (ceph_vino_is_reserved(vino))
+		return NULL;
+
 	/*
 	 * NB: The hashval will be run through the fs/inode.c hash function
 	 * anyway, so there is no need to squash the inode number down to
diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index e41a811026f6..3c90ae21a7e1 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -27,9 +27,10 @@ 
 #define CEPH_MONC_PROTOCOL   15 /* server/client */
 
 
-#define CEPH_INO_ROOT   1
-#define CEPH_INO_CEPH   2       /* hidden .ceph dir */
-#define CEPH_INO_DOTDOT 3	/* used by ceph fuse for parent (..) */
+#define CEPH_INO_ROOT			1 /* root inode number for all cephfs's */
+#define CEPH_INO_CEPH			2 /* hidden .ceph dir */
+#define CEPH_INO_GLOBAL_SNAPREALM	3 /* includes all snapshots in the fs */
+#define CEPH_INO_LOST_AND_FOUND		4 /* lost+found dir */
 
 /* arbitrary limit on max # of monitors (cluster of 3 is typical) */
 #define CEPH_MAX_MON   31