fuse: add a flag FUSE_OPEN_KILL_SUIDGID for open() request

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>

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 778367d..5d43af1 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -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;

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index aa0a44f..3498853 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -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;

diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 9eb96e0..98ca64d 100644 (file)
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -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 {