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fs: add a new SB_I_NOUMASK flag

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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@kernel.org>
Message-Id: <20230911-acl-fix-v3-1-b25315333f6c@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jeff Layton 2023-09-11 20:25:50 -04:00 committed by Christian Brauner
parent 84d2b69623
commit 5aa8fd9cea
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
5 changed files with 29 additions and 25 deletions
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6
fs/init.c
View File

@ -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,

19
fs/namei.c
View File

@ -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

2
fs/nfs/super.c
View File

@ -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;

3
include/linux/fs.h
View File

@ -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 {

24
include/linux/namei.h
View File

@ -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)