Commit e408e695 authored by Theodore Ts'o's avatar Theodore Ts'o Committed by Andrew Morton
Browse files

mm/shmem: support FS_IOC_[SG]ETFLAGS in tmpfs 

This allows userspace to set flags like FS_APPEND_FL, FS_IMMUTABLE_FL,
FS_NODUMP_FL, etc., like all other standard Linux file systems.

[akpm@linux-foundation.org: fix CONFIG_TMPFS_XATTR=n warnings]
Link: https://lkml.kernel.org/r/20220715015912.2560575-1-tytso@mit.edu


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 188043c7

include/linux/shmem_fs.h

+11 −0
Original line number Diff line number Diff line
@@ -25,9 +25,20 @@ struct shmem_inode_info { 
	struct simple_xattrs	xattrs;		/* list of xattrs */

	atomic_t		stop_eviction;	/* hold when working on inode */

	struct timespec64	i_crtime;	/* file creation time */

	unsigned int		fsflags;	/* flags for FS_IOC_[SG]ETFLAGS */

	struct inode		vfs_inode;

};



#define SHMEM_FL_USER_VISIBLE FS_FL_USER_VISIBLE

#define SHMEM_FL_USER_MODIFIABLE FS_FL_USER_MODIFIABLE

#define SHMEM_FL_INHERITED FS_FL_USER_MODIFIABLE



/* Flags that are appropriate for regular files (all but dir-specific ones). */

#define SHMEM_REG_FLMASK (~(FS_DIRSYNC_FL | FS_TOPDIR_FL))



/* Flags that are appropriate for non-directories/regular files. */

#define SHMEM_OTHER_FLMASK (FS_NODUMP_FL | FS_NOATIME_FL)



struct shmem_sb_info {

	unsigned long max_blocks;   /* How many blocks are allowed */

	struct percpu_counter used_blocks;  /* How many are allocated */

mm/shmem.c

+63 −1
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/ramfs.h>

#include <linux/pagemap.h>

#include <linux/file.h>

#include <linux/fileattr.h>

#include <linux/mm.h>

#include <linux/random.h>

#include <linux/sched/signal.h>
@@ -1058,6 +1059,15 @@ static int shmem_getattr(struct user_namespace *mnt_userns, 
		shmem_recalc_inode(inode);

		spin_unlock_irq(&info->lock);

	}

	if (info->fsflags & FS_APPEND_FL)

		stat->attributes |= STATX_ATTR_APPEND;

	if (info->fsflags & FS_IMMUTABLE_FL)

		stat->attributes |= STATX_ATTR_IMMUTABLE;

	if (info->fsflags & FS_NODUMP_FL)

		stat->attributes |= STATX_ATTR_NODUMP;

	stat->attributes_mask |= (STATX_ATTR_APPEND |

			STATX_ATTR_IMMUTABLE |

			STATX_ATTR_NODUMP);

	generic_fillattr(&init_user_ns, inode, stat);



	if (shmem_is_huge(NULL, inode, 0))
@@ -2272,7 +2282,18 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) 
	return 0;

}



static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,

/* Mask out flags that are inappropriate for the given type of inode. */

static unsigned shmem_mask_flags(umode_t mode, __u32 flags)

{

	if (S_ISDIR(mode))

		return flags;

	else if (S_ISREG(mode))

		return flags & SHMEM_REG_FLMASK;

	else

		return flags & SHMEM_OTHER_FLMASK;

}



static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,

				     umode_t mode, dev_t dev, unsigned long flags)

{

	struct inode *inode;
@@ -2297,6 +2318,9 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode 
		info->seals = F_SEAL_SEAL;

		info->flags = flags & VM_NORESERVE;

		info->i_crtime = inode->i_mtime;

		info->fsflags = (dir == NULL) ? 0 :

			SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;

		info->fsflags = shmem_mask_flags(mode, info->fsflags);

		INIT_LIST_HEAD(&info->shrinklist);

		INIT_LIST_HEAD(&info->swaplist);

		simple_xattrs_init(&info->xattrs);
@@ -3138,6 +3162,40 @@ static const char *shmem_get_link(struct dentry *dentry, 
}



#ifdef CONFIG_TMPFS_XATTR



static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)

{

	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));



	fileattr_fill_flags(fa, info->fsflags & SHMEM_FL_USER_VISIBLE);



	return 0;

}



static int shmem_fileattr_set(struct user_namespace *mnt_userns,

			      struct dentry *dentry, struct fileattr *fa)

{

	struct inode *inode = d_inode(dentry);

	struct shmem_inode_info *info = SHMEM_I(inode);



	if (fileattr_has_fsx(fa))

		return -EOPNOTSUPP;



	info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |

		(fa->flags & SHMEM_FL_USER_MODIFIABLE);



	inode->i_flags &= ~(S_APPEND | S_IMMUTABLE | S_NOATIME);

	if (info->fsflags & FS_APPEND_FL)

		inode->i_flags |= S_APPEND;

	if (info->fsflags & FS_IMMUTABLE_FL)

		inode->i_flags |= S_IMMUTABLE;

	if (info->fsflags & FS_NOATIME_FL)

		inode->i_flags |= S_NOATIME;



	inode->i_ctime = current_time(inode);

	return 0;

}



/*

 * Superblocks without xattr inode operations may get some security.* xattr

 * support from the LSM "for free". As soon as we have any other xattrs
@@ -3828,6 +3886,8 @@ static const struct inode_operations shmem_inode_operations = { 
#ifdef CONFIG_TMPFS_XATTR

	.listxattr	= shmem_listxattr,

	.set_acl	= simple_set_acl,

	.fileattr_get	= shmem_fileattr_get,

	.fileattr_set	= shmem_fileattr_set,

#endif

};
@@ -3847,6 +3907,8 @@ static const struct inode_operations shmem_dir_inode_operations = { 
#endif

#ifdef CONFIG_TMPFS_XATTR

	.listxattr	= shmem_listxattr,

	.fileattr_get	= shmem_fileattr_get,

	.fileattr_set	= shmem_fileattr_set,

#endif

#ifdef CONFIG_TMPFS_POSIX_ACL

	.setattr	= shmem_setattr,