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authorAlexei Starovoitov <ast@kernel.org>2023-04-10 19:43:44 +0200
committerAlexei Starovoitov <ast@kernel.org>2023-04-12 17:36:23 -0700
commitd319f344561de23e810515d109c7278919bff7b0 (patch)
treedcf462af3e03dbdc495b91ba633a4b9214e54dbb /mm/maccess.c
parentbbc73e6855b80144cd43d165696f1ff56d6192c9 (diff)
mm: Fix copy_from_user_nofault().
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>
Diffstat (limited to 'mm/maccess.c')
-rw-r--r--mm/maccess.c16
1 files changed, 11 insertions, 5 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
index 074f6b086671..518a25667323 100644
--- 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;