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mm: Fix copy_from_user_nofault().

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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@uci.edu>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Florian Lehner <dev@der-flo.net>
Tested-by: Hsin-Wei Hung <hsinweih@uci.edu>
Tested-by: Florian Lehner <dev@der-flo.net>
Link: https://lore.kernel.org/r/20230410174345.4376-2-dev@der-flo.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2023-04-10 19:43:44 +02:00
parent bbc73e6855
commit d319f34456
2 changed files with 12 additions and 6 deletions
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16
mm/maccess.c
View File

@ -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;

2
mm/usercopy.c
View File

@ -173,7 +173,7 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
return;
}
if (is_vmalloc_addr(ptr)) {
if (is_vmalloc_addr(ptr) && !pagefault_disabled()) {
struct vmap_area *area = find_vmap_area(addr);
if (!area)