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fuse: add a flag FUSE_OPEN_KILL_SUIDGID for open() request

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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_SUIDGID to fuse_open_in request which tells
server to kill suid/sgid (only if group execute is set).

This flag is added to the FUSE_OPEN request, as well as the FUSE_CREATE
request if the create was non-exclusive, since that might result in an
existing file being opened/truncated.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Vivek Goyal 2020-10-09 14:15:11 -04:00 committed by Miklos Szeredi
parent 8981bdfda7
commit 643a666a89
3 changed files with 21 additions and 2 deletions
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6
fs/fuse/dir.c
View file

@ -541,6 +541,12 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
inarg.flags = flags;
inarg.mode = mode;
inarg.umask = current_umask();
if (fm->fc->handle_killpriv_v2 && (flags & O_TRUNC) &&
!(flags & O_EXCL) && !capable(CAP_FSETID)) {
inarg.open_flags |= FUSE_OPEN_KILL_SUIDGID;
}
args.opcode = FUSE_CREATE;
args.nodeid = get_node_id(dir);
args.in_numargs = 2;

6
fs/fuse/file.c
View file

@ -42,6 +42,12 @@ static int fuse_send_open(struct fuse_mount *fm, u64 nodeid, struct file *file,
inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
if (!fm->fc->atomic_o_trunc)
inarg.flags &= ~O_TRUNC;
if (fm->fc->handle_killpriv_v2 &&
(inarg.flags & O_TRUNC) && !capable(CAP_FSETID)) {
inarg.open_flags |= FUSE_OPEN_KILL_SUIDGID;
}
args.opcode = opcode;
args.nodeid = nodeid;
args.in_numargs = 1;

11
include/uapi/linux/fuse.h
View file

@ -178,6 +178,7 @@
*
* 7.33
* - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID, FATTR_KILL_SUIDGID
* - add FUSE_OPEN_KILL_SUIDGID
*/
#ifndef _LINUX_FUSE_H
@ -444,6 +445,12 @@ struct fuse_file_lock {
*/
#define FUSE_ATTR_SUBMOUNT (1 << 0)
/**
* Open flags
* FUSE_OPEN_KILL_SUIDGID: Kill suid and sgid if executable
*/
#define FUSE_OPEN_KILL_SUIDGID (1 << 0)
enum fuse_opcode {
FUSE_LOOKUP = 1,
FUSE_FORGET = 2, /* no reply */
@ -605,14 +612,14 @@ struct fuse_setattr_in {
struct fuse_open_in {
uint32_t flags;
uint32_t unused;
uint32_t open_flags; /* FUSE_OPEN_... */
};
struct fuse_create_in {
uint32_t flags;
uint32_t mode;
uint32_t umask;
uint32_t padding;
uint32_t open_flags; /* FUSE_OPEN_... */
};
struct fuse_open_out {