Patch "ext4: Don't clear SGID when inheriting ACLs" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ext4: Don't clear SGID when inheriting ACLs

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ext4-don-t-clear-sgid-when-inheriting-acls.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jan Kara <[email protected]>
Date: Sun, 30 Jul 2017 23:33:01 -0400
Subject: ext4: Don't clear SGID when inheriting ACLs

From: Jan Kara <[email protected]>

commit a3bb2d5587521eea6dab2d05326abb0afb460abd upstream.

When new directory 'DIR1' is created in a directory 'DIR0' with SGID bit set, DIR1 is expected to have SGID bit set (and owning group equal to the owning group of 'DIR0'). However when 'DIR0' also has some default ACLs that 'DIR1' inherits, setting these ACLs will result in SGID bit on 'DIR1' to get cleared if user is not member of the owning group.

Fix the problem by moving posix_acl_update_mode() out of __ext4_set_acl() into ext4_set_acl(). That way the function will not be called when inheriting ACLs which is what we want as it prevents SGID bit clearing and the mode has been properly set by posix_acl_create() anyway.

---
 fs/ext4/acl.c |   22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

@@ -192,13 +192,6 @@ __ext4_set_acl(handle_t *handle, struct
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
-		if (acl) {
-			error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
-			if (error)
-				return error;
-			inode->i_ctime = ext4_current_time(inode);
-			ext4_mark_inode_dirty(handle, inode);
-		}
 		break;
 
 	case ACL_TYPE_DEFAULT:

@@ -231,6 +224,8 @@ ext4_set_acl(struct inode *inode, struct
 {
 	handle_t *handle;
 	int error, retries = 0;
+	umode_t mode = inode->i_mode;
+	int update_mode = 0;
 
 retry:
 	handle = ext4_journal_start(inode, EXT4_HT_XATTR,

@@ -238,7 +233,20 @@ retry:
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 
+	if ((type == ACL_TYPE_ACCESS) && acl) {
+		error = posix_acl_update_mode(inode, &mode, &acl);
+		if (error)
+			goto out_stop;
+		update_mode = 1;
+	}
+
 	error = __ext4_set_acl(handle, inode, type, acl);
+	if (!error && update_mode) {
+		inode->i_mode = mode;
+		inode->i_ctime = ext4_current_time(inode);
+		ext4_mark_inode_dirty(handle, inode);
+	}
+out_stop:
 	ext4_journal_stop(handle);
 	if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
 		goto retry;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ext4-fix-data-corruption-for-mmap-writes.patch queue-4.9/ext4-don-t-clear-sgid-when-inheriting-acls.patch