From: KP Singh <kpsingh@chromium.org>
Date: Thu, 4 Jun 2020 23:50:11 +0000 (-0700)
Subject: lib: Add might_fault() to strncpy_from_user.
X-Git-Tag: v5.10.7~2446^2~51
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=07887358993d48571f0f3a25cfce715564b35587;p=platform%2Fkernel%2Flinux-rpi.git

lib: Add might_fault() to strncpy_from_user.

When updating a piece of broken logic from using get_user to
strncpy_from_user, we noticed that a warning which is expected when
calling a function that might fault from an atomic context with
pagefaults enabled disappeared.

Not having this warning in place can lead to calling strncpy_from_user
from an atomic context and eventually kernel crashes/stack corruption.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jann Horn <jannh@google.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20200414225705.255711-1-kpsingh@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index b90ec55..34696a3 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -98,6 +98,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 {
 	unsigned long max_addr, src_addr;
 
+	might_fault();
 	if (unlikely(count <= 0))
 		return 0;