[076/127] lib: Add might_fault() to strncpy_from_user.

Commit Message

Andrew Morton June 4, 2020, 11:50 p.m. UTC

From: KP Singh <[e-mail]>
Subject: lib: Add might_fault() to strncpy_from_user.

From: KP Singh <[e-mail]>

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.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: KP Singh <[e-mail]>
Reviewed-by: Andrew Morton <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 lib/strncpy_from_user.c |    1 +
 1 file changed, 1 insertion(+)

Patch

--- a/lib/strncpy_from_user.c~lib-add-might_fault-to-strncpy_from_user
+++ a/lib/strncpy_from_user.c
@@ -98,6 +98,7 @@  long strncpy_from_user(char *dst, const
 {
 	unsigned long max_addr, src_addr;
 
+	might_fault();
 	if (unlikely(count <= 0))
 		return 0;