summaryrefslogtreecommitdiff
path: root/fs/fuse
diff options
context:
space:
mode:
authorVivek Goyal <vgoyal@redhat.com>2020-10-09 21:15:07 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2020-11-11 19:22:32 +0300
commit63f9909ff602082597849f684655e93336c50b11 (patch)
treeb6826e7dde35148fc24c0049818491f72b0aac9e /fs/fuse
parentdf8629af293493757beccac2d3168fe5a315636e (diff)
downloadlinux-63f9909ff602082597849f684655e93336c50b11.tar.xz
fuse: introduce the notion of FUSE_HANDLE_KILLPRIV_V2
We already have FUSE_HANDLE_KILLPRIV flag that says that file server will remove suid/sgid/caps on truncate/chown/write. But that's little different from what Linux VFS implements. To be consistent with Linux VFS behavior what we want is. - caps are always cleared on chown/write/truncate - suid is always cleared on chown, while for truncate/write it is cleared only if caller does not have CAP_FSETID. - sgid is always cleared on chown, while for truncate/write it is cleared only if caller does not have CAP_FSETID as well as file has group execute permission. As previous flag did not provide above semantics. Implement a V2 of the protocol with above said constraints. Server does not know if caller has CAP_FSETID or not. So for the case of write()/truncate(), client will send information in special flag to indicate whether to kill priviliges or not. These changes are in subsequent patches. FUSE_HANDLE_KILLPRIV_V2 relies on WRITE being sent to server to clear suid/sgid/security.capability. But with ->writeback_cache, WRITES are cached in guest. So it is not recommended to use FUSE_HANDLE_KILLPRIV_V2 and writeback_cache together. Though it probably might be good enough for lot of use cases. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/fuse_i.h8
-rw-r--r--fs/fuse/inode.c5
2 files changed, 12 insertions, 1 deletions
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 8301c5056022..d414c787e362 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -636,6 +636,14 @@ struct fuse_conn {
unsigned int legacy_opts_show:1;
/*
+ * fs kills suid/sgid/cap on write/chown/trunc. suid is killed on
+ * write/trunc only if caller did not have CAP_FSETID. sgid is killed
+ * on write/truncate only if caller did not have CAP_FSETID as well as
+ * file has group execute permission.
+ */
+ unsigned handle_killpriv_v2:1;
+
+ /*
* The following bitfields are only for optimization purposes
* and hence races in setting them will not cause malfunction
*/
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e7e9005b9b66..5a6102cd6473 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1038,6 +1038,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
!fuse_dax_check_alignment(fc, arg->map_alignment)) {
ok = false;
}
+ if (arg->flags & FUSE_HANDLE_KILLPRIV_V2)
+ fc->handle_killpriv_v2 = 1;
} else {
ra_pages = fc->max_read / PAGE_SIZE;
fc->no_lock = 1;
@@ -1080,7 +1082,8 @@ void fuse_send_init(struct fuse_mount *fm)
FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
- FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA;
+ FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
+ FUSE_HANDLE_KILLPRIV_V2;
#ifdef CONFIG_FUSE_DAX
if (fm->fc->dax)
ia->in.flags |= FUSE_MAP_ALIGNMENT;