With FUSE_HANDLE_KILLPRIV_V2 support, server will need to kill
suid/sgid/security.capability on open(O_TRUNC), if server supports
FUSE_ATOMIC_O_TRUNC.
But server needs to kill suid/sgid only if caller does not have
CAP_FSETID. Given server does not have this information, client
needs to send this info to server.
So add a flag FUSE_OPEN_KILL_PRIV to fuse_open_in request which tells
server to kill suid/sgid(only if group execute is set).
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/fuse/file.c | 5 +++++
include/uapi/linux/fuse.h | 10 +++++++++-
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e40428f3d0f1..2853f55fd8f7 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -42,6 +42,11 @@ static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
if (!fc->atomic_o_trunc)
inarg.flags &= ~O_TRUNC;
+
+ if (fc->handle_killpriv_v2 && (inarg.flags & O_TRUNC) &&
+ !capable(CAP_FSETID))
+ inarg.open_flags |= FUSE_OPEN_KILL_PRIV;
+
args.opcode = opcode;
args.nodeid = nodeid;
args.in_numargs = 1;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 7b8da0a2de0d..e20b3ee9d292 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -173,6 +173,7 @@
* - add FUSE_SETUPMAPPING and FUSE_REMOVEMAPPING
* - add map_alignment to fuse_init_out, add FUSE_MAP_ALIGNMENT flag
* - add FUSE_HANDLE_KILLPRIV_V2
+ * - add FUSE_OPEN_KILL_PRIV
*/
#ifndef _LINUX_FUSE_H
@@ -427,6 +428,13 @@ struct fuse_file_lock {
*/
#define FUSE_FSYNC_FDATASYNC (1 << 0)
+/**
+ * Open flags
+ * FUSE_OPEN_KILL_PRIV: Kill suid/sgid/security.capability. sgid is cleared
+ * only if file has group execute permission.
+ */
+#define FUSE_OPEN_KILL_PRIV (1 << 0)
+
enum fuse_opcode {
FUSE_LOOKUP = 1,
FUSE_FORGET = 2, /* no reply */
@@ -588,7 +596,7 @@ struct fuse_setattr_in {
struct fuse_open_in {
uint32_t flags;
- uint32_t unused;
+ uint32_t open_flags;
};
struct fuse_create_in {
--
2.25.4
