The patch titled
Subject: userfaultfd/sysctl: add vm.unprivileged_userfaultfd
has been added to the -mm tree. Its filename is
userfaultfd-sysctl-add-vmunprivileged_userfaultfd.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-sysctl-add-vmunprivileged_userfaultfd.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-sysctl-add-vmunprivileged_userfaultfd.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: userfaultfd/sysctl: add vm.unprivileged_userfaultfd
Add a global sysctl knob "vm.unprivileged_userfaultfd" to control
whether userfaultfd is allowed by unprivileged users. When this is
set to zero, only privileged users (root user, or users with the
CAP_SYS_PTRACE capability) will be able to use the userfaultfd
syscalls.
Link: http://lkml.kernel.org/r/20190319030722.12441-2-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Suggested-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>
Cc: Maya Gokhale <gokhale2@xxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Martin Cracauer <cracauer@xxxxxxxx>
Cc: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>
Cc: Marty McFadden <mcfadden8@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 12 ++++++++++++
fs/userfaultfd.c | 5 +++++
include/linux/userfaultfd_k.h | 2 ++
kernel/sysctl.c | 12 ++++++++++++
4 files changed, 31 insertions(+)
--- a/Documentation/sysctl/vm.txt~userfaultfd-sysctl-add-vmunprivileged_userfaultfd
+++ a/Documentation/sysctl/vm.txt
@@ -61,6 +61,7 @@ Currently, these files are in /proc/sys/
- stat_refresh
- numa_stat
- swappiness
+- unprivileged_userfaultfd
- user_reserve_kbytes
- vfs_cache_pressure
- watermark_boost_factor
@@ -818,6 +819,17 @@ The default value is 60.
==============================================================
+unprivileged_userfaultfd
+
+This flag controls whether unprivileged users can use the userfaultfd
+syscalls. Set this to 1 to allow unprivileged users to use the
+userfaultfd syscalls, or set this to 0 to restrict userfaultfd to only
+privileged users (with SYS_CAP_PTRACE capability).
+
+The default value is 1.
+
+==============================================================
+
- user_reserve_kbytes
When overcommit_memory is set to 2, "never overcommit" mode, reserve
--- a/fs/userfaultfd.c~userfaultfd-sysctl-add-vmunprivileged_userfaultfd
+++ a/fs/userfaultfd.c
@@ -30,6 +30,8 @@
#include <linux/security.h>
#include <linux/hugetlb.h>
+int sysctl_unprivileged_userfaultfd __read_mostly = 1;
+
static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
enum userfaultfd_state {
@@ -1921,6 +1923,9 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
struct userfaultfd_ctx *ctx;
int fd;
+ if (!sysctl_unprivileged_userfaultfd && !capable(CAP_SYS_PTRACE))
+ return -EPERM;
+
BUG_ON(!current->mm);
/* Check the UFFD_* constants for consistency. */
--- a/include/linux/userfaultfd_k.h~userfaultfd-sysctl-add-vmunprivileged_userfaultfd
+++ a/include/linux/userfaultfd_k.h
@@ -28,6 +28,8 @@
#define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
#define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS)
+extern int sysctl_unprivileged_userfaultfd;
+
extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
--- a/kernel/sysctl.c~userfaultfd-sysctl-add-vmunprivileged_userfaultfd
+++ a/kernel/sysctl.c
@@ -66,6 +66,7 @@
#include <linux/kexec.h>
#include <linux/bpf.h>
#include <linux/mount.h>
+#include <linux/userfaultfd_k.h>
#include "../lib/kstrtox.h"
@@ -1719,6 +1720,17 @@ static struct ctl_table vm_table[] = {
.extra2 = (void *)&mmap_rnd_compat_bits_max,
},
#endif
+#ifdef CONFIG_USERFAULTFD
+ {
+ .procname = "unprivileged_userfaultfd",
+ .data = &sysctl_unprivileged_userfaultfd,
+ .maxlen = sizeof(sysctl_unprivileged_userfaultfd),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+#endif
{ }
};
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
userfaultfd-sysctl-add-vmunprivileged_userfaultfd.patch
