Commit b08c8fc0 authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

bpf: Re-support uid and gid when mounting bpffs 



For a clean, conflict-free revert of the token-related patches in commit
d17aff80 ("Revert BPF token-related functionality"), the bpf fs commit
750e7857 ("bpf: Support uid and gid when mounting bpffs") was undone
temporarily as well.

This patch manually re-adds the functionality from the original one back
in 750e7857, no other functional changes intended.

Testing:

  # mount -t bpf -o uid=65534,gid=65534 bpffs ./foo
  # ls -la . | grep foo
  drwxrwxrwt   2 nobody nogroup          0 Dec 20 13:16 foo
  # mount -t bpf
  bpffs on /root/foo type bpf (rw,relatime,uid=65534,gid=65534)

Also, passing invalid arguments for uid/gid are properly rejected as expected.

Fixes: d17aff80 ("Revert BPF token-related functionality")
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Cc: Jie Jiang <jiejiang@chromium.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/bpf/20231220133805.20953-1-daniel@iogearbox.net
parent fc3a5534

kernel/bpf/inode.c

+51 −2
Original line number Diff line number Diff line
@@ -599,8 +599,15 @@ EXPORT_SYMBOL(bpf_prog_get_type_path); 
 */

static int bpf_show_options(struct seq_file *m, struct dentry *root)

{

	umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;



	struct inode *inode = d_inode(root);

	umode_t mode = inode->i_mode & S_IALLUGO & ~S_ISVTX;



	if (!uid_eq(inode->i_uid, GLOBAL_ROOT_UID))

		seq_printf(m, ",uid=%u",

			   from_kuid_munged(&init_user_ns, inode->i_uid));

	if (!gid_eq(inode->i_gid, GLOBAL_ROOT_GID))

		seq_printf(m, ",gid=%u",

			   from_kgid_munged(&init_user_ns, inode->i_gid));

	if (mode != S_IRWXUGO)

		seq_printf(m, ",mode=%o", mode);

	return 0;
@@ -625,15 +632,21 @@ static const struct super_operations bpf_super_ops = { 
};



enum {

	OPT_UID,

	OPT_GID,

	OPT_MODE,

};



static const struct fs_parameter_spec bpf_fs_parameters[] = {

	fsparam_u32	("uid",				OPT_UID),

	fsparam_u32	("gid",				OPT_GID),

	fsparam_u32oct	("mode",			OPT_MODE),

	{}

};



struct bpf_mount_opts {

	kuid_t uid;

	kgid_t gid;

	umode_t mode;

};
@@ -641,6 +654,8 @@ static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param) 
{

	struct bpf_mount_opts *opts = fc->fs_private;

	struct fs_parse_result result;

	kuid_t uid;

	kgid_t gid;

	int opt;



	opt = fs_parse(fc, bpf_fs_parameters, param, &result);
@@ -662,12 +677,42 @@ static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param) 
	}



	switch (opt) {

	case OPT_UID:

		uid = make_kuid(current_user_ns(), result.uint_32);

		if (!uid_valid(uid))

			goto bad_value;



		/*

		 * The requested uid must be representable in the

		 * filesystem's idmapping.

		 */

		if (!kuid_has_mapping(fc->user_ns, uid))

			goto bad_value;



		opts->uid = uid;

		break;

	case OPT_GID:

		gid = make_kgid(current_user_ns(), result.uint_32);

		if (!gid_valid(gid))

			goto bad_value;



		/*

		 * The requested gid must be representable in the

		 * filesystem's idmapping.

		 */

		if (!kgid_has_mapping(fc->user_ns, gid))

			goto bad_value;



		opts->gid = gid;

		break;

	case OPT_MODE:

		opts->mode = result.uint_32 & S_IALLUGO;

		break;

	}



	return 0;

bad_value:

	return invalfc(fc, "Bad value for '%s'", param->key);

}



struct bpf_preload_ops *bpf_preload_ops;
@@ -750,6 +795,8 @@ static int bpf_fill_super(struct super_block *sb, struct fs_context *fc) 
	sb->s_op = &bpf_super_ops;



	inode = sb->s_root->d_inode;

	inode->i_uid = opts->uid;

	inode->i_gid = opts->gid;

	inode->i_op = &bpf_dir_iops;

	inode->i_mode &= ~S_IALLUGO;

	populate_bpffs(sb->s_root);
@@ -785,6 +832,8 @@ static int bpf_init_fs_context(struct fs_context *fc) 
		return -ENOMEM;



	opts->mode = S_IRWXUGO;

	opts->uid = current_fsuid();

	opts->gid = current_fsgid();



	fc->fs_private = opts;

	fc->ops = &bpf_context_ops;