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Message-ID: <20250321194230.1928571-1-sdl@nppct.ru>
Date: Fri, 21 Mar 2025 19:42:26 +0000
From: Alexey Nepomnyashih <sdl@...ct.ru>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Alexey Nepomnyashih <sdl@...ct.ru>,
Jeremy Kerr <jk@...abs.org>,
linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org,
lvc-project@...uxtesting.org,
Jiao Zhou <jiaozhou@...gle.com>,
Matthew Garrett <mgarrett@...ora.tech>
Subject: [PATCH 6.1 v2 1/2] efivarfs: Add uid/gid mount options
From: Jiao Zhou <jiaozhou@...gle.com>
commit 5329aa5101f73c451bcd48deaf3f296685849d9c upstream.
Allow UEFI variables to be modified by non-root processes in order to
run sandboxed code. This doesn't change the behavior of mounting
efivarfs unless uid/gid are specified; by default both are set to root.
Signed-off-by: Jiao Zhou <jiaozhou@...gle.com>
Acked-by: Matthew Garrett <mgarrett@...ora.tech>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Alexey Nepomnyashih <sdl@...ct.ru>
---
fs/efivarfs/inode.c | 4 +++
fs/efivarfs/internal.h | 9 ++++++
fs/efivarfs/super.c | 68 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 81 insertions(+)
diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
index b3dc7ff42400..e93f2afd6741 100644
--- a/fs/efivarfs/inode.c
+++ b/fs/efivarfs/inode.c
@@ -21,8 +21,12 @@ struct inode *efivarfs_get_inode(struct super_block *sb,
dev_t dev, bool is_removable)
{
struct inode *inode = new_inode(sb);
+ struct efivarfs_fs_info *fsi = sb->s_fs_info;
+ struct efivarfs_mount_opts *opts = &fsi->mount_opts;
if (inode) {
+ inode->i_uid = opts->uid;
+ inode->i_gid = opts->gid;
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
diff --git a/fs/efivarfs/internal.h b/fs/efivarfs/internal.h
index dcb973d8736c..0762c0a1d207 100644
--- a/fs/efivarfs/internal.h
+++ b/fs/efivarfs/internal.h
@@ -9,6 +9,15 @@
#include <linux/list.h>
#include <linux/efi.h>
+struct efivarfs_mount_opts {
+ kuid_t uid;
+ kgid_t gid;
+};
+
+struct efivarfs_fs_info {
+ struct efivarfs_mount_opts mount_opts;
+};
+
struct efi_variable {
efi_char16_t VariableName[EFI_VAR_NAME_LEN/sizeof(efi_char16_t)];
efi_guid_t VendorGuid;
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index b8c4641ed152..b4f1c46ea06f 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -8,6 +8,7 @@
#include <linux/efi.h>
#include <linux/fs.h>
#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/ucs2_string.h>
@@ -24,10 +25,26 @@ static void efivarfs_evict_inode(struct inode *inode)
clear_inode(inode);
}
+static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
+{
+ struct super_block *sb = root->d_sb;
+ struct efivarfs_fs_info *sbi = sb->s_fs_info;
+ struct efivarfs_mount_opts *opts = &sbi->mount_opts;
+
+ if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
+ seq_printf(m, ",uid=%u",
+ from_kuid_munged(&init_user_ns, opts->uid));
+ if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
+ seq_printf(m, ",gid=%u",
+ from_kgid_munged(&init_user_ns, opts->gid));
+ return 0;
+}
+
static const struct super_operations efivarfs_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.evict_inode = efivarfs_evict_inode,
+ .show_options = efivarfs_show_options,
};
/*
@@ -183,6 +200,45 @@ static int efivarfs_destroy(struct efivar_entry *entry, void *data)
return 0;
}
+enum {
+ Opt_uid, Opt_gid,
+};
+
+static const struct fs_parameter_spec efivarfs_parameters[] = {
+ fsparam_u32("uid", Opt_uid),
+ fsparam_u32("gid", Opt_gid),
+ {},
+};
+
+static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+ struct efivarfs_fs_info *sbi = fc->s_fs_info;
+ struct efivarfs_mount_opts *opts = &sbi->mount_opts;
+ struct fs_parse_result result;
+ int opt;
+
+ opt = fs_parse(fc, efivarfs_parameters, param, &result);
+ if (opt < 0)
+ return opt;
+
+ switch (opt) {
+ case Opt_uid:
+ opts->uid = make_kuid(current_user_ns(), result.uint_32);
+ if (!uid_valid(opts->uid))
+ return -EINVAL;
+ break;
+ case Opt_gid:
+ opts->gid = make_kgid(current_user_ns(), result.uint_32);
+ if (!gid_valid(opts->gid))
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct inode *inode = NULL;
@@ -236,11 +292,22 @@ static int efivarfs_reconfigure(struct fs_context *fc)
static const struct fs_context_operations efivarfs_context_ops = {
.get_tree = efivarfs_get_tree,
+ .parse_param = efivarfs_parse_param,
.reconfigure = efivarfs_reconfigure,
};
static int efivarfs_init_fs_context(struct fs_context *fc)
{
+ struct efivarfs_fs_info *sfi;
+
+ sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
+ if (!sfi)
+ return -ENOMEM;
+
+ sfi->mount_opts.uid = GLOBAL_ROOT_UID;
+ sfi->mount_opts.gid = GLOBAL_ROOT_GID;
+
+ fc->s_fs_info = sfi;
fc->ops = &efivarfs_context_ops;
return 0;
}
@@ -261,6 +328,7 @@ static struct file_system_type efivarfs_type = {
.name = "efivarfs",
.init_fs_context = efivarfs_init_fs_context,
.kill_sb = efivarfs_kill_sb,
+ .parameters = efivarfs_parameters,
};
static __init int efivarfs_init(void)
--
2.43.0
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