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* [PATCH] ceph: take reference to req->r_parent at point of assignment
@ 2021-06-18 17:39 Jeff Layton
  2021-06-21 11:51 ` Luis Henriques
  0 siblings, 1 reply; 3+ messages in thread
From: Jeff Layton @ 2021-06-18 17:39 UTC (permalink / raw)
  To: ceph-devel; +Cc: idryomov

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@kernel.org>
---
 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;
 	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


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] ceph: take reference to req->r_parent at point of assignment
  2021-06-18 17:39 [PATCH] ceph: take reference to req->r_parent at point of assignment Jeff Layton
@ 2021-06-21 11:51 ` Luis Henriques
  2021-06-21 12:03   ` Jeff Layton
  0 siblings, 1 reply; 3+ messages in thread
From: Luis Henriques @ 2021-06-21 11:51 UTC (permalink / raw)
  To: Jeff Layton; +Cc: ceph-devel, idryomov

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@kernel.org>
> ---
>  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@suse.de>

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
> 


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] ceph: take reference to req->r_parent at point of assignment
  2021-06-21 11:51 ` Luis Henriques
@ 2021-06-21 12:03   ` Jeff Layton
  0 siblings, 0 replies; 3+ messages in thread
From: Jeff Layton @ 2021-06-21 12:03 UTC (permalink / raw)
  To: Luis Henriques; +Cc: ceph-devel, idryomov

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@kernel.org>
> > ---
> >  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@suse.de>
> 

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@kernel.org>


^ permalink raw reply	[flat|nested] 3+ messages in thread
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2021-06-18 17:39 [PATCH] ceph: take reference to req->r_parent at point of assignment Jeff Layton
2021-06-21 11:51 ` Luis Henriques
2021-06-21 12:03   ` Jeff Layton

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