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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: Theodore Ts'o <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Theodore Ts'o 2022-07-14 21:59:12 -04:00 committed by akpm
parent 188043c7f4
commit e408e695f5
2 changed files with 74 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/shmem_fs.h
View File

@ -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 */

64
mm/shmem.c
View File

@ -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,