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 <jiejiang@chromium.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Mike Frysinger <vapier@chromium.org>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231212093923.497838-1-jiejiang@chromium.org

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0bd4889e917a3f252ecbbd4874b975993f9284ae..c87c608a3689230b6208be9dd3fde2018f8859d9 100644 (file)
--- 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 5359a0929c35d75149ead1c543521e1587bc6bc7..0a8e1188ea46e5ab954fc4200f3e14887d2c2971 100644 (file)
--- 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;