[PATCH 6.3 006/199] mm: Fix copy_from_user_nofault().

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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)





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