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ANDROID: fuse: allow mounting with no userspace daemon

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This is useful for testing fuse-bpf directly on a backing folder.

Bug: 217570523
Test: mount -t fuse [DEVNAME] [mntpoint] -o user_id=0,group_id=0,rootmode=0040000,
             no_daemon,root_dir=[backingfd]
Change-Id: I9ac13c3f707d71cbb74dba10eda5778bf3e83233
Signed-off-by: Daniel Rosenberg <drosen@google.com>
This commit is contained in:
Daniel Rosenberg
2022-01-27 16:53:22 -08:00
parent 7b87bbebf9
commit 23c9fbd407
2 changed files with 30 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
fs/fuse/fuse_i.h
View File

@@ -544,6 +544,7 @@ struct fuse_fs_context {
bool no_force_umount:1;
bool legacy_opts_show:1;
bool dax:1;
bool no_daemon:1;
unsigned int max_read;
unsigned int blksize;
const char *subtype;
@@ -792,6 +793,9 @@ struct fuse_conn {
/** Passthrough mode for read/write IO */
unsigned int passthrough:1;
/** BPF Only, no Daemon running */
unsigned int no_daemon:1;
/** The number of requests waiting for completion */
atomic_t num_waiting;

40
fs/fuse/inode.c
View File

@@ -598,6 +598,7 @@ enum {
OPT_BLKSIZE,
OPT_ROOT_BPF,
OPT_ROOT_DIR,
OPT_NO_DAEMON,
OPT_ERR
};
@@ -614,6 +615,7 @@ static const struct fs_parameter_spec fuse_fs_parameters[] = {
fsparam_string ("subtype", OPT_SUBTYPE),
fsparam_u32 ("root_bpf", OPT_ROOT_BPF),
fsparam_u32 ("root_dir", OPT_ROOT_DIR),
fsparam_flag ("no_daemon", OPT_NO_DAEMON),
{}
};
@@ -712,6 +714,11 @@ static int fuse_parse_param(struct fs_context *fc, struct fs_parameter *param)
return invalfc(fc, "Unable to open root directory");
break;
case OPT_NO_DAEMON:
ctx->no_daemon = true;
ctx->fd_present = true;
break;
default:
return -EINVAL;
}
@@ -1267,7 +1274,7 @@ void fuse_send_init(struct fuse_mount *fm)
ia->args.nocreds = true;
ia->args.end = process_init_reply;
if (fuse_simple_background(fm, &ia->args, GFP_KERNEL) != 0)
if (unlikely(fm->fc->no_daemon) || fuse_simple_background(fm, &ia->args, GFP_KERNEL) != 0)
process_init_reply(fm, &ia->args, -ENOTCONN);
}
EXPORT_SYMBOL_GPL(fuse_send_init);
@@ -1513,6 +1520,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
fc->destroy = ctx->destroy;
fc->no_control = ctx->no_control;
fc->no_force_umount = ctx->no_force_umount;
fc->no_daemon = ctx->no_daemon;
err = -ENOMEM;
root = fuse_get_root_inode(sb, ctx->rootmode, ctx->root_bpf,
@@ -1564,18 +1572,20 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
struct fuse_mount *fm;
err = -EINVAL;
file = fget(ctx->fd);
if (!file)
goto err;
if (!ctx->no_daemon) {
file = fget(ctx->fd);
if (!file)
goto err;
/*
* Require mount to happen from the same user namespace which
* opened /dev/fuse to prevent potential attacks.
*/
if ((file->f_op != &fuse_dev_operations) ||
(file->f_cred->user_ns != sb->s_user_ns))
goto err_fput;
ctx->fudptr = &file->private_data;
/*
* Require mount to happen from the same user namespace which
* opened /dev/fuse to prevent potential attacks.
*/
if ((file->f_op != &fuse_dev_operations) ||
(file->f_cred->user_ns != sb->s_user_ns))
goto err_fput;
ctx->fudptr = &file->private_data;
}
fc = kmalloc(sizeof(*fc), GFP_KERNEL);
err = -ENOMEM;
@@ -1601,7 +1611,8 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
* memory barrier for file->private_data to be visible on all
* CPUs after this
*/
fput(file);
if (!ctx->no_daemon)
fput(file);
fuse_send_init(get_fuse_mount_super(sb));
return 0;
@@ -1609,7 +1620,8 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
fuse_mount_put(fm);
sb->s_fs_info = NULL;
err_fput:
fput(file);
if (!ctx->no_daemon)
fput(file);
err:
return err;
}