From 750e785796bb72423b97cac21ecd0fa3b3b65610 Mon Sep 17 00:00:00 2001
From: Jie Jiang <jiejiang@chromium.org>
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 <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
---
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 0bd4889e917a3..c87c608a36892 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 5359a0929c35d..0a8e1188ea46e 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;
--
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