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105ff5339f
The new MFD_NOEXEC_SEAL and MFD_EXEC flags allows application to set
executable bit at creation time (memfd_create).
When MFD_NOEXEC_SEAL is set, memfd is created without executable bit
(mode:0666), and sealed with F_SEAL_EXEC, so it can't be chmod to be
executable (mode: 0777) after creation.
when MFD_EXEC flag is set, memfd is created with executable bit
(mode:0777), this is the same as the old behavior of memfd_create.
The new pid namespaced sysctl vm.memfd_noexec has 3 values:
0: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL acts like
MFD_EXEC was set.
1: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL acts like
MFD_NOEXEC_SEAL was set.
2: memfd_create() without MFD_NOEXEC_SEAL will be rejected.
The sysctl allows finer control of memfd_create for old-software that
doesn't set the executable bit, for example, a container with
vm.memfd_noexec=1 means the old-software will create non-executable memfd
by default. Also, the value of memfd_noexec is passed to child namespace
at creation time. For example, if the init namespace has
vm.memfd_noexec=2, all its children namespaces will be created with 2.
[akpm@linux-foundation.org: add stub functions to fix build]
[akpm@linux-foundation.org: remove unneeded register_pid_ns_ctl_table_vm() stub, per Jeff]
[akpm@linux-foundation.org: s/pr_warn_ratelimited/pr_warn_once/, per review]
[akpm@linux-foundation.org: fix CONFIG_SYSCTL=n warning]
Link: https://lkml.kernel.org/r/20221215001205.51969-4-jeffxu@google.com
Signed-off-by: Jeff Xu <jeffxu@google.com>
Co-developed-by: Daniel Verkamp <dverkamp@chromium.org>
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef LINUX_PID_SYSCTL_H
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#define LINUX_PID_SYSCTL_H
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#include <linux/pid_namespace.h>
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
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static inline void initialize_memfd_noexec_scope(struct pid_namespace *ns)
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{
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ns->memfd_noexec_scope =
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task_active_pid_ns(current)->memfd_noexec_scope;
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}
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static int pid_mfd_noexec_dointvec_minmax(struct ctl_table *table,
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int write, void *buf, size_t *lenp, loff_t *ppos)
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{
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struct pid_namespace *ns = task_active_pid_ns(current);
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struct ctl_table table_copy;
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if (write && !ns_capable(ns->user_ns, CAP_SYS_ADMIN))
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return -EPERM;
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table_copy = *table;
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if (ns != &init_pid_ns)
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table_copy.data = &ns->memfd_noexec_scope;
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/*
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* set minimum to current value, the effect is only bigger
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* value is accepted.
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*/
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if (*(int *)table_copy.data > *(int *)table_copy.extra1)
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table_copy.extra1 = table_copy.data;
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return proc_dointvec_minmax(&table_copy, write, buf, lenp, ppos);
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}
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static struct ctl_table pid_ns_ctl_table_vm[] = {
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{
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.procname = "memfd_noexec",
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.data = &init_pid_ns.memfd_noexec_scope,
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.maxlen = sizeof(init_pid_ns.memfd_noexec_scope),
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.mode = 0644,
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.proc_handler = pid_mfd_noexec_dointvec_minmax,
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.extra1 = SYSCTL_ZERO,
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.extra2 = SYSCTL_TWO,
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},
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{ }
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};
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static struct ctl_path vm_path[] = { { .procname = "vm", }, { } };
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static inline void register_pid_ns_sysctl_table_vm(void)
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{
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register_sysctl_paths(vm_path, pid_ns_ctl_table_vm);
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}
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#else
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static inline void initialize_memfd_noexec_scope(struct pid_namespace *ns) {}
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static inline void set_memfd_noexec_scope(struct pid_namespace *ns) {}
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static inline void register_pid_ns_sysctl_table_vm(void) {}
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#endif
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#endif /* LINUX_PID_SYSCTL_H */
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