From 550a7d3bc0c4049ef8d36ff4d9ed7082ee8cb5ec Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Thu, 25 Mar 2021 11:18:23 -0400
Subject: fuse: add a flag FUSE_SETXATTR_ACL_KILL_SGID to kill SGID
When posix access ACL is set, it can have an effect on file mode and it can
also need to clear SGID if.
- None of caller's group/supplementary groups match file owner group.
AND
- Caller is not priviliged (No CAP_FSETID).
As of now fuser server is responsible for changing the file mode as
well. But it does not know whether to clear SGID or not.
So add a flag FUSE_SETXATTR_ACL_KILL_SGID and send this info with SETXATTR
to let file server know that sgid needs to be cleared as well.
Reported-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/fuse/acl.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
(limited to 'fs/fuse')
diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index d31260a139d4..52b165319be1 100644
--- a/fs/fuse/acl.c
+++ b/fs/fuse/acl.c
@@ -71,6 +71,7 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
return -EINVAL;
if (acl) {
+ unsigned int extra_flags = 0;
/*
* Fuse userspace is responsible for updating access
* permissions in the inode, if needed. fuse_setxattr
@@ -94,7 +95,11 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
return ret;
}
- ret = fuse_setxattr(inode, name, value, size, 0, 0);
+ if (!in_group_p(i_gid_into_mnt(&init_user_ns, inode)) &&
+ !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))
+ extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
+
+ ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);
kfree(value);
} else {
ret = fuse_removexattr(inode, name);
--
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