4.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
commit fd3220d37b1f6f0cab6142d98b0e6c4082e63299 upstream.
This change fixes xfstest generic/375, which failed to clear the
setgid bit in the following test case on overlayfs:
touch $testfile
chown 100:100 $testfile
chmod 2755 $testfile
_runas -u 100 -g 101 -- setfacl -m u::rwx,g::rwx,o::rwx $testfile
Reported-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Tested-by: Amir Goldstein <amir73il@xxxxxxxxx>
Fixes: d837a49bd57f ("ovl: fix POSIX ACL setting")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/overlayfs/super.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1026,6 +1026,21 @@ ovl_posix_acl_xattr_set(const struct xat
posix_acl_release(acl);
+ /*
+ * Check if sgid bit needs to be cleared (actual setacl operation will
+ * be done with mounter's capabilities and so that won't do it for us).
+ */
+ if (unlikely(inode->i_mode & S_ISGID) &&
+ handler->flags == ACL_TYPE_ACCESS &&
+ !in_group_p(inode->i_gid) &&
+ !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
+ struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+ err = ovl_setattr(dentry, &iattr);
+ if (err)
+ return err;
+ }
+
err = ovl_xattr_set(dentry, handler->name, value, size, flags);
if (!err)
ovl_copyattr(ovl_inode_real(inode, NULL), inode);
--
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