[PATCH 3/3] fuse: Add a flag FUSE_SETXATTR_ACL_KILL_SGID to kill SGID
From: Vivek Goyal <vgoyal@redhat.com>
Date: 2021-03-19 19:57:17
Also in:
lkml
Subsystem:
filesystems (vfs and infrastructure), fuse filesystem [core], the rest · Maintainers:
Alexander Viro, Christian Brauner, Miklos Szeredi, Linus Torvalds
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 <redacted> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> --- fs/fuse/acl.c | 7 ++++++- include/uapi/linux/fuse.h | 7 +++++++ 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index d31260a139d4..45358124181a 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 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 (fc->setxattr_v2 && + posix_acl_mode_clear_sgid(&init_user_ns, inode)) + 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);
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 1bb555c1c117..08c11a7beaa7 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h@@ -180,6 +180,7 @@ * - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID, FATTR_KILL_SUIDGID * - add FUSE_OPEN_KILL_SUIDGID * - add FUSE_SETXATTR_V2 + * - add FUSE_SETXATTR_ACL_KILL_SGID */ #ifndef _LINUX_FUSE_H
@@ -454,6 +455,12 @@ struct fuse_file_lock { */ #define FUSE_OPEN_KILL_SUIDGID (1 << 0) +/** + * setxattr flags + * FUSE_SETXATTR_ACL_KILL_SGID: Clear SGID when system.posix_acl_access is set + */ +#define FUSE_SETXATTR_ACL_KILL_SGID (1 << 0) + enum fuse_opcode { FUSE_LOOKUP = 1, FUSE_FORGET = 2, /* no reply */
--
2.25.4