FUSE_HANDLE_KILLPRIV flag says that file server will remove suid/sgid/caps on truncate/chown/write.
But to be consistent with 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. Signed-off-by: Vivek Goyal <[email protected]> --- fs/fuse/fuse_i.h | 6 ++++++ fs/fuse/inode.c | 5 ++++- include/uapi/linux/fuse.h | 7 +++++++ 3 files changed, 17 insertions(+), 1 deletion(-) diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 740a8a7d7ae6..71bede0a57c9 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -610,6 +610,12 @@ struct fuse_conn { /** cache READLINK responses in page cache */ unsigned cache_symlinks: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 bba747520e9b..113ba149e08d 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -965,6 +965,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_args *args, min_t(unsigned int, FUSE_MAX_MAX_PAGES, max_t(unsigned int, arg->max_pages, 1)); } + if (arg->flags & FUSE_HANDLE_KILLPRIV_V2) + fc->handle_killpriv_v2 = 1; } else { ra_pages = fc->max_read / PAGE_SIZE; fc->no_lock = 1; @@ -1002,7 +1004,8 @@ void fuse_send_init(struct fuse_conn *fc) 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; ia->args.opcode = FUSE_INIT; ia->args.in_numargs = 1; ia->args.in_args[0].size = sizeof(ia->in); diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 373cada89815..960ba8af5cf4 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -172,6 +172,7 @@ * - add FUSE_WRITE_KILL_PRIV flag * - add FUSE_SETUPMAPPING and FUSE_REMOVEMAPPING * - add map_alignment to fuse_init_out, add FUSE_MAP_ALIGNMENT flag + * - add FUSE_HANDLE_KILLPRIV_V2 */ #ifndef _LINUX_FUSE_H @@ -314,6 +315,11 @@ struct fuse_file_lock { * FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir * FUSE_EXPLICIT_INVAL_DATA: only invalidate cached pages on explicit request * FUSE_MAP_ALIGNMENT: map_alignment field is valid + * FUSE_HANDLE_KILLPRIV_V2: fs kills suid/sgid/cap on write/chown/trunc. + * Upon write/truncate suid/sgid is only killed if caller + * does not have CAP_FSETID. Additionally upon + * write/truncate sgid is killed only if file has group + * execute permission. (Same as Linux VFS behavior). */ #define FUSE_ASYNC_READ (1 << 0) #define FUSE_POSIX_LOCKS (1 << 1) @@ -342,6 +348,7 @@ struct fuse_file_lock { #define FUSE_NO_OPENDIR_SUPPORT (1 << 24) #define FUSE_EXPLICIT_INVAL_DATA (1 << 25) #define FUSE_MAP_ALIGNMENT (1 << 26) +#define FUSE_HANDLE_KILLPRIV_V2 (1 << 27) /** * CUSE INIT request/reply flags -- 2.25.4 _______________________________________________ Virtio-fs mailing list [email protected] https://www.redhat.com/mailman/listinfo/virtio-fs
