From 750e785796bb72423b97cac21ecd0fa3b3b65610 Mon Sep 17 00:00:00 2001 From: Jie Jiang Date: Tue, 12 Dec 2023 09:39:23 +0000 Subject: [PATCH] bpf: Support uid and gid when mounting bpffs Parse uid and gid in bpf_parse_param() so that they can be passed in as the `data` parameter when mount() bpffs. This will be useful when we want to control which user/group has the control to the mounted bpffs, otherwise a separate chown() call will be needed. Signed-off-by: Jie Jiang Signed-off-by: Andrii Nakryiko Acked-by: Mike Frysinger Acked-by: Christian Brauner Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20231212093923.497838-1-jiejiang@chromium.org --- include/linux/bpf.h | 2 ++ kernel/bpf/inode.c | 50 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 51 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 0bd4889e917a..c87c608a3689 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1595,6 +1595,8 @@ struct bpf_link_primer { }; struct bpf_mount_opts { + kuid_t uid; + kgid_t gid; umode_t mode; /* BPF token-related delegation options */ diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 5359a0929c35..0a8e1188ea46 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -601,9 +601,16 @@ EXPORT_SYMBOL(bpf_prog_get_type_path); static int bpf_show_options(struct seq_file *m, struct dentry *root) { struct bpf_mount_opts *opts = root->d_sb->s_fs_info; - 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; u64 mask; + 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); @@ -652,6 +659,8 @@ const struct super_operations bpf_super_ops = { }; enum { + OPT_UID, + OPT_GID, OPT_MODE, OPT_DELEGATE_CMDS, OPT_DELEGATE_MAPS, @@ -660,6 +669,8 @@ enum { }; static const struct fs_parameter_spec bpf_fs_parameters[] = { + fsparam_u32 ("uid", OPT_UID), + fsparam_u32 ("gid", OPT_GID), fsparam_u32oct ("mode", OPT_MODE), fsparam_string ("delegate_cmds", OPT_DELEGATE_CMDS), fsparam_string ("delegate_maps", OPT_DELEGATE_MAPS), @@ -672,6 +683,8 @@ static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct bpf_mount_opts *opts = fc->s_fs_info; struct fs_parse_result result; + kuid_t uid; + kgid_t gid; int opt, err; u64 msk; @@ -694,6 +707,34 @@ 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; @@ -722,6 +763,9 @@ static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param) } return 0; + +bad_value: + return invalfc(fc, "Bad value for '%s'", param->key); } struct bpf_preload_ops *bpf_preload_ops; @@ -808,6 +852,8 @@ 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); @@ -843,6 +889,8 @@ static int bpf_init_fs_context(struct fs_context *fc) return -ENOMEM; opts->mode = S_IRWXUGO; + opts->uid = current_fsuid(); + opts->gid = current_fsgid(); /* start out with no BPF token delegation enabled */ opts->delegate_cmds = 0; -- 2.20.1