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fs: namei: Allow follow_down() to uncover auto mounts 

This function is only used by NFSD to cross mount points.
If a mount point is of type auto mount, follow_down() will
not uncover it. Add LOOKUP_AUTOMOUNT to the lookup flags
to have ->d_automount() called when NFSD walks down the
mount tree.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Ian Kent <raven@themaw.net>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Richard Weinberger 2022-12-07 09:43:08 +01:00 committed by Chuck Lever
parent 50f5fdaea9
commit e1f19857f9
3 changed files with 9 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
fs/namei.c
View File

@ -1458,11 +1458,11 @@ EXPORT_SYMBOL(follow_down_one);
* point, the filesystem owning that dentry may be queried as to whether the
* caller is permitted to proceed or not.
*/
int follow_down(struct path *path)
int follow_down(struct path *path, unsigned int flags)
{
struct vfsmount *mnt = path->mnt;
bool jumped;
int ret = traverse_mounts(path, &jumped, NULL, 0);
int ret = traverse_mounts(path, &jumped, NULL, flags);
if (path->mnt != mnt)
mntput(mnt);
@ -2864,7 +2864,7 @@ int path_pts(struct path *path)
path->dentry = child;
dput(parent);
follow_down(path);
follow_down(path, 0);
return 0;
}
#endif

6
fs/nfsd/vfs.c
View File

@ -126,9 +126,13 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
struct dentry *dentry = *dpp;
struct path path = {.mnt = mntget(exp->ex_path.mnt),
.dentry = dget(dentry)};
unsigned int follow_flags = 0;
int err = 0;
err = follow_down(&path);
if (exp->ex_flags & NFSEXP_CROSSMOUNT)
follow_flags = LOOKUP_AUTOMOUNT;
err = follow_down(&path, follow_flags);
if (err < 0)
goto out;
if (path.mnt == exp->ex_path.mnt && path.dentry == dentry &&

2
include/linux/namei.h
View File

@ -77,7 +77,7 @@ struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
struct dentry *base, int len);
extern int follow_down_one(struct path *);
extern int follow_down(struct path *);
extern int follow_down(struct path *path, unsigned int flags);
extern int follow_up(struct path *);
extern struct dentry *lock_rename(struct dentry *, struct dentry *);