alios: fs,ext4: remove projid limit when create hard link

This is a temporary workaround plan to avoid the limitation when
creating hard link cross two projids.
Signed-off-by: Nzhangliguang <zhangliguang@linux.alibaba.com>
Reviewed-by: NLiu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

Documentation/sysctl/fs.txt

@@ -36,6 +36,7 @@ Currently, these files are in /proc/sys/fs:
 - pipe-user-pages-soft
 - protected_fifos
 - protected_hardlinks
+- hardlink_cross_projid
 - protected_regular
 - protected_symlinks
 - suid_dumpable
@@ -238,6 +239,15 @@ When set to "2" it also applies to group writable sticky directories.
 
 ==============================================================
 
+hardlink_cross_projid:
+
+This is a temporary workaround plan to avoid the limitation when creating
+hard link cross two projids. When set to "0", hardlink creation cross
+two projids is restricted. When set to "1" hardlinks can be created
+cross two projids.
+
+==============================================================
+
 protected_symlinks:
 
 A long-standing class of security issues is the symlink-based

fs/ext4/namei.c

@@ -3225,7 +3225,8 @@ static int ext4_link(struct dentry *old_dentry,
 	if (err)
 		return err;
 
-	if ((ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT)) &&
+	if (!sysctl_hardlink_cross_projid &&
+	    (ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT)) &&
 	    (!projid_eq(EXT4_I(dir)->i_projid,
 			EXT4_I(old_dentry->d_inode)->i_projid)))
 		return -EXDEV;

include/linux/fs.h

@@ -74,6 +74,7 @@ extern struct inodes_stat_t inodes_stat;
 extern int leases_enable, lease_break_time;
 extern int sysctl_protected_symlinks;
 extern int sysctl_protected_hardlinks;
+extern int sysctl_hardlink_cross_projid;
 extern int sysctl_protected_fifos;
 extern int sysctl_protected_regular;
 

kernel/sys.c

@@ -144,6 +144,9 @@ int fs_overflowgid = DEFAULT_FS_OVERFLOWGID;
 EXPORT_SYMBOL(fs_overflowuid);
 EXPORT_SYMBOL(fs_overflowgid);
 
+int sysctl_hardlink_cross_projid = 0;
+EXPORT_SYMBOL(sysctl_hardlink_cross_projid);
+
 /*
  * Returns true if current's euid is same as p's uid or euid,
  * or has CAP_SYS_NICE to p's user_ns.

kernel/sysctl.c

@@ -1874,6 +1874,15 @@ static struct ctl_table fs_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &one,
 	},
+	{
+		.procname	= "hardlink_cross_projid",
+		.data		= &sysctl_hardlink_cross_projid,
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &one,
+	},
 	{ }
 };