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Message-ID: <2961dcb0-ddf3-b9f0-3268-12a4ff996856@google.com>
Date: Wed, 10 Aug 2022 21:51:09 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Theodore Ts'o <tytso@....edu>, Radoslaw Burny <rburny@...gle.com>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH] mm/shmem: fix chattr fsflags support in tmpfs
ext[234] have always allowed unimplemented chattr flags to be set,
but other filesystems have tended to be stricter. Follow the stricter
approach for tmpfs: I don't want to have to explain why csu attributes
don't actually work, and we won't need to update the chattr(1) manpage;
and it's never wrong to start off strict, relaxing later if persuaded.
Allow only a (append only) i (immutable) A (no atime) and d (no dump).
Although lsattr showed 'A' inherited, the NOATIME behavior was not
being inherited: because nothing sync'ed FS_NOATIME_FL to S_NOATIME.
Add shmem_set_inode_flags() to sync the flags, using inode_set_flags()
to avoid that instant of lost immutablility during fileattr_set().
But that change switched generic/079 from passing to failing: because
FS_IMMUTABLE_FL and FS_APPEND_FL had been unconventionally included in
the INHERITED fsflags: remove them and generic/079 is back to passing.
Fixes: e408e695f5f1 ("mm/shmem: support FS_IOC_[SG]ETFLAGS in tmpfs")
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
include/linux/shmem_fs.h | 13 +++-------
mm/shmem.c | 54 +++++++++++++++++++++++-----------------
2 files changed, 35 insertions(+), 32 deletions(-)
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -29,15 +29,10 @@ struct shmem_inode_info {
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)
+#define SHMEM_FL_USER_VISIBLE FS_FL_USER_VISIBLE
+#define SHMEM_FL_USER_MODIFIABLE \
+ (FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL | FS_NOATIME_FL)
+#define SHMEM_FL_INHERITED (FS_NODUMP_FL | FS_NOATIME_FL)
struct shmem_sb_info {
unsigned long max_blocks; /* How many blocks are allowed */
diff --git a/mm/shmem.c b/mm/shmem.c
index e975fcd9d2e1..bd9b114a8650 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2281,16 +2281,34 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
return 0;
}
-/* Mask out flags that are inappropriate for the given type of inode. */
-static unsigned shmem_mask_flags(umode_t mode, __u32 flags)
+#ifdef CONFIG_TMPFS_XATTR
+static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
+
+/*
+ * chattr's fsflags are unrelated to extended attributes,
+ * but tmpfs has chosen to enable them under the same config option.
+ */
+static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
+{
+ unsigned int i_flags = 0;
+
+ if (fsflags & FS_NOATIME_FL)
+ i_flags |= S_NOATIME;
+ if (fsflags & FS_APPEND_FL)
+ i_flags |= S_APPEND;
+ if (fsflags & FS_IMMUTABLE_FL)
+ i_flags |= S_IMMUTABLE;
+ /*
+ * But FS_NODUMP_FL does not require any action in i_flags.
+ */
+ inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE);
+}
+#else
+static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
{
- if (S_ISDIR(mode))
- return flags;
- else if (S_ISREG(mode))
- return flags & SHMEM_REG_FLMASK;
- else
- return flags & SHMEM_OTHER_FLMASK;
}
+#define shmem_initxattrs NULL
+#endif
static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
umode_t mode, dev_t dev, unsigned long flags)
@@ -2319,7 +2337,8 @@ static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
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);
+ if (info->fsflags)
+ shmem_set_inode_flags(inode, info->fsflags);
INIT_LIST_HEAD(&info->shrinklist);
INIT_LIST_HEAD(&info->swaplist);
simple_xattrs_init(&info->xattrs);
@@ -2468,12 +2487,6 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
static const struct inode_operations shmem_symlink_inode_operations;
static const struct inode_operations shmem_short_symlink_operations;
-#ifdef CONFIG_TMPFS_XATTR
-static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
-#else
-#define shmem_initxattrs NULL
-#endif
-
static int
shmem_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len,
@@ -3179,18 +3192,13 @@ static int shmem_fileattr_set(struct user_namespace *mnt_userns,
if (fileattr_has_fsx(fa))
return -EOPNOTSUPP;
+ if (fa->flags & ~SHMEM_FL_USER_MODIFIABLE)
+ 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;
-
+ shmem_set_inode_flags(inode, info->fsflags);
inode->i_ctime = current_time(inode);
return 0;
}
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