Re: Umask ignored when mounting NFSv4.2 share of an exported Filesystem with noacl (was: Re: Bug#962254: NFS(v4) broken at 4.19.118-2)

[Andreas Gruenbacher <agruenba@redhat.com>]

Hi Bruce,

On Wed, Jun 17, 2020 at 2:58 AM J. Bruce Fields <bfields@redhat.com> wrote:
> I think I'll send the following upstream.

looking good, but how about using a little helper for this?

Also I'm not sure if ecryptfs gets this right, so taking the ecryptfs
list into the CC.

Thanks,
Andreas

--

Add a posix_acl_apply_umask helper for filesystems like nfsd to apply
the umask before calling into vfs_create, vfs_mkdir, and vfs_mknod when
necessary.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/namei.c                |  9 +++------
 fs/nfsd/vfs.c             |  6 ++----
 fs/overlayfs/dir.c        |  4 ++--
 fs/posix_acl.c            | 15 +++++++++++++++
 include/linux/posix_acl.h |  6 ++++++
 5 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 72d4219c93ac..a68887d3a446 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3054,8 +3054,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 	if (open_flag & O_CREAT) {
 		if (open_flag & O_EXCL)
 			open_flag &= ~O_TRUNC;
-		if (!IS_POSIXACL(dir->d_inode))
-			mode &= ~current_umask();
+		posix_acl_apply_umask(dir->d_inode, &mode);
 		if (likely(got_write))
 			create_error = may_o_create(&nd->path, dentry, mode);
 		else
@@ -3580,8 +3579,7 @@ long do_mknodat(int dfd, const char __user *filename, umode_t mode,
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	if (!IS_POSIXACL(path.dentry->d_inode))
-		mode &= ~current_umask();
+	posix_acl_apply_umask(path.dentry->d_inode, &mode);
 	error = security_path_mknod(&path, dentry, mode, dev);
 	if (error)
 		goto out;
@@ -3657,8 +3655,7 @@ long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	if (!IS_POSIXACL(path.dentry->d_inode))
-		mode &= ~current_umask();
+	posix_acl_apply_umask(path.dentry->d_inode, &mode);
 	error = security_path_mkdir(&path, dentry, mode);
 	if (!error)
 		error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index d22a056da477..0c625b004b0c 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1226,8 +1226,7 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		iap->ia_mode = 0;
 	iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
 
-	if (!IS_POSIXACL(dirp))
-		iap->ia_mode &= ~current_umask();
+	posix_acl_apply_umask(dirp, &iap->ia_mode);
 
 	err = 0;
 	host_err = 0;
@@ -1461,8 +1460,7 @@ do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		goto out;
 	}
 
-	if (!IS_POSIXACL(dirp))
-		iap->ia_mode &= ~current_umask();
+	posix_acl_apply_umask(dirp, &iap->ia_mode);
 
 	host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
 	if (host_err < 0) {
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1bba4813f9cb..4d98db2a0208 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -325,8 +325,8 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 	struct dentry *newdentry;
 	int err;
 
-	if (!attr->hardlink && !IS_POSIXACL(udir))
-		attr->mode &= ~current_umask();
+	if (!attr->hardlink)
+	       posix_acl_apply_umask(udir, &attr->mode);
 
 	inode_lock_nested(udir, I_MUTEX_PARENT);
 	newdentry = ovl_create_real(udir,
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 95882b3f5f62..7ee647b74bc2 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -578,6 +578,21 @@ posix_acl_chmod(struct inode *inode, umode_t mode)
 }
 EXPORT_SYMBOL(posix_acl_chmod);
 
+/*
+ * On inode creation, filesystems with ACL support are expected to apply the
+ * umask when no ACL is inherited from the parent directory; this is usually
+ * done by posix_acl_create.  Filesystems like nfsd that call vfs_create,
+ * vfs_mknod, or vfs_mkdir directly are expected to call posix_acl_apply_umask
+ * to apply the umask first when necessary.
+ */
+void
+posix_acl_apply_umask(struct inode *inode, umode_t *mode)
+{
+	if (!IS_POSIXACL(inode))
+		*mode &= ~current_umask();
+}
+EXPORT_SYMBOL(posix_acl_apply_umask);
+
 int
 posix_acl_create(struct inode *dir, umode_t *mode,
 		struct posix_acl **default_acl, struct posix_acl **acl)
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 90797f1b421d..76e402ff4f92 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -73,6 +73,7 @@ extern int set_posix_acl(struct inode *, int, struct posix_acl *);
 
 #ifdef CONFIG_FS_POSIX_ACL
 extern int posix_acl_chmod(struct inode *, umode_t);
+extern void posix_acl_apply_umask(struct inode *, umode_t *);
 extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
 		struct posix_acl **);
 extern int posix_acl_update_mode(struct inode *, umode_t *, struct posix_acl **);
@@ -99,6 +100,11 @@ static inline int posix_acl_chmod(struct inode *inode, umode_t mode)
 
 #define simple_set_acl		NULL
 
+static inline void posix_acl_apply_umask(struct inode *inode, umode_t *mode)
+{
+	*mode &= ~current_umask();
+}
+
 static inline int simple_acl_create(struct inode *dir, struct inode *inode)
 {
 	return 0;

base-commit: 69119673bd50b176ded34032fadd41530fb5af21
prerequisite-patch-id: a8319d40da9f70f478892d0bd8e63f540364b089
-- 
2.26.2