[PATCH 0/11 v1] Fix inheritance of SGID in presence of default ACLs

[PATCH 0/11 v1] Fix inheritance of SGID in presence of default ACLs

[Jan Kara]

Hello,

this patch set fixes a problem introduced by commit 073931017b49 "posix_acl:
Clear SGID bit when setting file permissions". The problem is that 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.

The problem is fixed by moving posix_acl_update_mode() so that it does not
get called when default ACLs are inherited.

I have created new generic/441 test for this and verified that generic/314,
generic/375, and generic/441 pass for ext2, ext4, btrfs, xfs, ocfs2, reiserfs.

All patches in this series are completely independent so fs maintainers please
pick them up as soon as they get reviewed. I'm leaving for three weeks of
vacation at the end of the week so I won't be able to push this further for
some time.

								Honza

[PATCH 03/11] btrfs: Don't clear SGID when inheriting ACLs

[Jan Kara]

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
__btrfs_set_acl() into btrfs_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.

Fixes: 073931017b49d9458aa351605b43a7e34598caef
CC: stable@vger.kernel.org
CC: linux-btrfs@vger.kernel.org
CC: David Sterba <dsterba@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/btrfs/acl.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 247b8dfaf6e5..8d8370ddb6b2 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -78,12 +78,6 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
-		if (acl) {
-			ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
-			if (ret)
-				return ret;
-		}
-		ret = 0;
 		break;
 	case ACL_TYPE_DEFAULT:
 		if (!S_ISDIR(inode->i_mode))
@@ -119,6 +113,13 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 
 int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
+	int ret;
+
+	if (type == ACL_TYPE_ACCESS && acl) {
+		ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+		if (ret)
+			return ret;
+	}
 	return __btrfs_set_acl(NULL, inode, acl, type);
 }
 
-- 
2.12.3

Re: [PATCH 03/11] btrfs: Don't clear SGID when inheriting ACLs

[David Sterba]

On Thu, Jun 22, 2017 at 03:31:07PM +0200, Jan Kara wrote:
> 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
> __btrfs_set_acl() into btrfs_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.
> 
> Fixes: 073931017b49d9458aa351605b43a7e34598caef
> CC: stable@vger.kernel.org
> CC: linux-btrfs@vger.kernel.org
> CC: David Sterba <dsterba@suse.com>
> Signed-off-by: Jan Kara <jack@suse.cz>

Added to btrfs patch queue, thanks.