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ovl: Prevent rw remount when it should be ro mount 

Overlayfs should be mounted read-only when upper-fs is read-only or nonexistent.
But now it can be remounted read-write and this can cause kernel panic.
So we should prevent read-write remount when the above situation happens.

Signed-off-by: Seunghun Lee <waydi1@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Seunghun Lee 2015-01-03 02:26:49 +09:00 committed by Miklos Szeredi
parent a425c037f3
commit 3cdf6fe910
1 changed files with 12 additions and 0 deletions
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12
fs/overlayfs/super.c
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@ -525,10 +525,22 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
return 0;
}
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
struct ovl_fs *ufs = sb->s_fs_info;
if (!(*flags & MS_RDONLY) &&
(!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
return -EROFS;
return 0;
}
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
.remount_fs = ovl_remount,
};
enum {