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    Subject[patch 10/10] allow unprivileged fuse mounts
    From: Miklos Szeredi <mszeredi@suse.cz>

    Use FS_SAFE for "fuse" fs type, but not for "fuseblk".

    FUSE was designed from the beginning to be safe for unprivileged
    users. This has also been verified in practice over many years. In
    addition unprivileged fuse mounts require the "usermnt" mount option
    to be set on the parent mount, which is more strict than the current
    userspace policy.

    This will enable future installations to remove the suid-root
    fusermount utility.

    Don't require the "user_id=" and "group_id=" options for unprivileged
    mounts, but if they are present, verify them for sanity.

    Disallow the "allow_other" option for unprivileged mounts.

    Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
    ---

    Index: linux/fs/fuse/inode.c
    ===================================================================
    --- linux.orig/fs/fuse/inode.c 2007-04-13 14:20:23.000000000 +0200
    +++ linux/fs/fuse/inode.c 2007-04-13 14:20:27.000000000 +0200
    @@ -311,6 +311,19 @@ static int parse_fuse_opt(char *opt, str
    d->max_read = ~0;
    d->blksize = 512;

    + /*
    + * For unprivileged mounts use current uid/gid. Still allow
    + * "user_id" and "group_id" options for compatibility, but
    + * only if they match these values.
    + */
    + if (!capable(CAP_SYS_ADMIN)) {
    + d->user_id = current->uid;
    + d->user_id_present = 1;
    + d->group_id = current->gid;
    + d->group_id_present = 1;
    +
    + }
    +
    while ((p = strsep(&opt, ",")) != NULL) {
    int token;
    int value;
    @@ -339,6 +352,8 @@ static int parse_fuse_opt(char *opt, str
    case OPT_USER_ID:
    if (match_int(&args[0], &value))
    return 0;
    + if (d->user_id_present && d->user_id != value)
    + return 0;
    d->user_id = value;
    d->user_id_present = 1;
    break;
    @@ -346,6 +361,8 @@ static int parse_fuse_opt(char *opt, str
    case OPT_GROUP_ID:
    if (match_int(&args[0], &value))
    return 0;
    + if (d->group_id_present && d->group_id != value)
    + return 0;
    d->group_id = value;
    d->group_id_present = 1;
    break;
    @@ -536,6 +553,10 @@ static int fuse_fill_super(struct super_
    if (!parse_fuse_opt((char *) data, &d, is_bdev))
    return -EINVAL;

    + /* This is a privileged option */
    + if ((d.flags & FUSE_ALLOW_OTHER) && !capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    if (is_bdev) {
    #ifdef CONFIG_BLOCK
    if (!sb_set_blocksize(sb, d.blksize))
    @@ -639,6 +660,7 @@ static struct file_system_type fuse_fs_t
    .fs_flags = FS_HAS_SUBTYPE,
    .get_sb = fuse_get_sb,
    .kill_sb = kill_anon_super,
    + .fs_flags = FS_SAFE,
    };

    #ifdef CONFIG_BLOCK
    --
    -
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