This is a note to let you know that I've just added the patch titled
mm: Fix copy_from_user_nofault().
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-fix-copy_from_user_nofault.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d319f344561de23e810515d109c7278919bff7b0 Mon Sep 17 00:00:00 2001
From: Alexei Starovoitov <ast@xxxxxxxxxx>
Date: Mon, 10 Apr 2023 19:43:44 +0200
Subject: mm: Fix copy_from_user_nofault().
From: Alexei Starovoitov <ast@xxxxxxxxxx>
commit d319f344561de23e810515d109c7278919bff7b0 upstream.
There are several issues with copy_from_user_nofault():
- access_ok() is designed for user context only and for that reason
it has WARN_ON_IN_IRQ() which triggers when bpf, kprobe, eprobe
and perf on ppc are calling it from irq.
- it's missing nmi_uaccess_okay() which is a nop on all architectures
except x86 where it's required.
The comment in arch/x86/mm/tlb.c explains the details why it's necessary.
Calling copy_from_user_nofault() from bpf, [ke]probe without this check is not safe.
- __copy_from_user_inatomic() under CONFIG_HARDENED_USERCOPY is calling
check_object_size()->__check_object_size()->check_heap_object()->find_vmap_area()->spin_lock()
which is not safe to do from bpf, [ke]probe and perf due to potential deadlock.
Fix all three issues. At the end the copy_from_user_nofault() becomes
equivalent to copy_from_user_nmi() from safety point of view with
a difference in the return value.
Reported-by: Hsin-Wei Hung <hsinweih@xxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Florian Lehner <dev@xxxxxxxxxxx>
Tested-by: Hsin-Wei Hung <hsinweih@xxxxxxx>
Tested-by: Florian Lehner <dev@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230410174345.4376-2-dev@xxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Javier Honduvilla Coto <javierhonduco@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/maccess.c | 16 +++++++++++-----
mm/usercopy.c | 2 +-
2 files changed, 12 insertions(+), 6 deletions(-)
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -5,6 +5,7 @@
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
+#include <asm/tlb.h>
bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
size_t size)
@@ -113,11 +114,16 @@ Efault:
long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
{
long ret = -EFAULT;
- if (access_ok(src, size)) {
- pagefault_disable();
- ret = __copy_from_user_inatomic(dst, src, size);
- pagefault_enable();
- }
+
+ if (!__access_ok(src, size))
+ return ret;
+
+ if (!nmi_uaccess_okay())
+ return ret;
+
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(dst, src, size);
+ pagefault_enable();
if (ret)
return -EFAULT;
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -173,7 +173,7 @@ static inline void check_heap_object(con
return;
}
- if (is_vmalloc_addr(ptr)) {
+ if (is_vmalloc_addr(ptr) && !pagefault_disabled()) {
struct vmap_area *area = find_vmap_area(addr);
if (!area)
Patches currently in stable-queue which might be from ast@xxxxxxxxxx are
queue-6.3/mm-fix-copy_from_user_nofault.patch
