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Message-Id: <20230911-acl-fix-v3-1-b25315333f6c@kernel.org>
Date: Mon, 11 Sep 2023 20:25:50 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Trond Myklebust <trond.myklebust@...merspace.com>,
Anna Schumaker <anna@...nel.org>,
Ondrej Valousek <ondrej.valousek.xm@...esas.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nfs@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v3] fs: add a new SB_I_NOUMASK flag
SB_POSIXACL must be set when a filesystem supports POSIX ACLs, but NFSv4
also sets this flag to prevent the VFS from applying the umask on
newly-created files. NFSv4 doesn't support POSIX ACLs however, which
causes confusion when other subsystems try to test for them.
Add a new SB_I_NOUMASK flag that allows filesystems to opt-in to umask
stripping without advertising support for POSIX ACLs. Set the new flag
on NFSv4 instead of SB_POSIXACL.
Also, move mode_strip_umask to namei.h and convert init_mknod and
init_mkdir to use it.
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
Yet another approach to fixing this issue. I think this way is probably
the best, since makes the purpose of these flags clearer, and stops NFS
from relying on SB_POSIXACL to avoid umask stripping.
---
Changes in v3:
- move new flag to s_iflags
- convert init_mkdir and init_mknod to use mode_strip_umask
- Link to v2: https://lore.kernel.org/r/20230910-acl-fix-v2-1-38d6caa81419@kernel.org
Changes in v2:
- new approach: add a new SB_NOUMASK flag that NFSv4 can use instead of
SB_POSIXACL
- Link to v1: https://lore.kernel.org/r/20230908-acl-fix-v1-1-1e6b76c8dcc8@kernel.org
---
fs/init.c | 6 ++----
fs/namei.c | 19 -------------------
fs/nfs/super.c | 2 +-
include/linux/fs.h | 3 ++-
include/linux/namei.h | 24 ++++++++++++++++++++++++
5 files changed, 29 insertions(+), 25 deletions(-)
diff --git a/fs/init.c b/fs/init.c
index 9684406a8416..e9387b6c4f30 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -153,8 +153,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (!IS_POSIXACL(path.dentry->d_inode))
- mode &= ~current_umask();
+ mode = mode_strip_umask(d_inode(path.dentry), mode);
error = security_path_mknod(&path, dentry, mode, dev);
if (!error)
error = vfs_mknod(mnt_idmap(path.mnt), path.dentry->d_inode,
@@ -229,8 +228,7 @@ int __init init_mkdir(const char *pathname, umode_t mode)
dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (!IS_POSIXACL(path.dentry->d_inode))
- mode &= ~current_umask();
+ mode = mode_strip_umask(d_inode(path.dentry), mode);
error = security_path_mkdir(&path, dentry, mode);
if (!error)
error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
diff --git a/fs/namei.c b/fs/namei.c
index 567ee547492b..94b27370f468 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3103,25 +3103,6 @@ void unlock_rename(struct dentry *p1, struct dentry *p2)
}
EXPORT_SYMBOL(unlock_rename);
-/**
- * mode_strip_umask - handle vfs umask stripping
- * @dir: parent directory of the new inode
- * @mode: mode of the new inode to be created in @dir
- *
- * Umask stripping depends on whether or not the filesystem supports POSIX
- * ACLs. If the filesystem doesn't support it umask stripping is done directly
- * in here. If the filesystem does support POSIX ACLs umask stripping is
- * deferred until the filesystem calls posix_acl_create().
- *
- * Returns: mode
- */
-static inline umode_t mode_strip_umask(const struct inode *dir, umode_t mode)
-{
- if (!IS_POSIXACL(dir))
- mode &= ~current_umask();
- return mode;
-}
-
/**
* vfs_prepare_mode - prepare the mode to be used for a new inode
* @idmap: idmap of the mount the inode was found from
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 0d6473cb00cb..9b1cfca8112a 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1071,7 +1071,7 @@ static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
sb->s_export_op = &nfs_export_ops;
break;
case 4:
- sb->s_flags |= SB_POSIXACL;
+ sb->s_iflags |= SB_I_NOUMASK;
sb->s_time_gran = 1;
sb->s_time_min = S64_MIN;
sb->s_time_max = S64_MAX;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4aeb3fa11927..58dea591a341 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1119,7 +1119,7 @@ extern int send_sigurg(struct fown_struct *fown);
#define SB_NOATIME BIT(10) /* Do not update access times. */
#define SB_NODIRATIME BIT(11) /* Do not update directory access times */
#define SB_SILENT BIT(15)
-#define SB_POSIXACL BIT(16) /* VFS does not apply the umask */
+#define SB_POSIXACL BIT(16) /* Supports POSIX ACLs */
#define SB_INLINECRYPT BIT(17) /* Use blk-crypto for encrypted files */
#define SB_KERNMOUNT BIT(22) /* this is a kern_mount call */
#define SB_I_VERSION BIT(23) /* Update inode I_version field */
@@ -1166,6 +1166,7 @@ extern int send_sigurg(struct fown_struct *fown);
#define SB_I_PERSB_BDI 0x00000200 /* has a per-sb bdi */
#define SB_I_TS_EXPIRY_WARNED 0x00000400 /* warned about timestamp range expiry */
#define SB_I_RETIRED 0x00000800 /* superblock shouldn't be reused */
+#define SB_I_NOUMASK 0x00001000 /* VFS does not apply umask */
/* Possible states of 'frozen' field */
enum {
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 1463cbda4888..e3619920f9f0 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -92,6 +92,30 @@ extern struct dentry *lock_rename(struct dentry *, struct dentry *);
extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
extern void unlock_rename(struct dentry *, struct dentry *);
+/**
+ * mode_strip_umask - handle vfs umask stripping
+ * @dir: parent directory of the new inode
+ * @mode: mode of the new inode to be created in @dir
+ *
+ * In most filesystems, umask stripping depends on whether or not the
+ * filesystem supports POSIX ACLs. If the filesystem doesn't support it umask
+ * stripping is done directly in here. If the filesystem does support POSIX
+ * ACLs umask stripping is deferred until the filesystem calls
+ * posix_acl_create().
+ *
+ * Some filesystems (like NFSv4) also want to avoid umask stripping by the
+ * VFS, but don't support POSIX ACLs. Those filesystems can set SB_I_NOUMASK
+ * to get this effect without declaring that they support POSIX ACLs.
+ *
+ * Returns: mode
+ */
+static inline umode_t __must_check mode_strip_umask(const struct inode *dir, umode_t mode)
+{
+ if (!IS_POSIXACL(dir) && !(dir->i_sb->s_iflags & SB_I_NOUMASK))
+ mode &= ~current_umask();
+ return mode;
+}
+
extern int __must_check nd_jump_link(const struct path *path);
static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
---
base-commit: a48fa7efaf1161c1c898931fe4c7f0070964233a
change-id: 20230908-acl-fix-6f8f86930f32
Best regards,
--
Jeff Layton <jlayton@...nel.org>
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