mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions
authorPeter Zijlstra <peterz@infradead.org>
Wed, 24 Apr 2019 07:19:25 +0000 (09:19 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 31 May 2019 13:46:16 +0000 (06:46 -0700)
commit189b396a2580d6174996edbd5f5bbbe1d34dd29f
tree2ae535714ed8a9829749fd1f63e5f87d3229ba6c
parentf46ae1cd7ceccd98f3d280d6771ba1e9d03acd8d
mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions

[ Upstream commit 29da93fea3ea39ab9b12270cc6be1b70ef201c9e ]

Randy reported objtool triggered on his (GCC-7.4) build:

  lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x315: call to __ubsan_handle_add_overflow() with UACCESS enabled
  lib/strnlen_user.o: warning: objtool: strnlen_user()+0x337: call to __ubsan_handle_sub_overflow() with UACCESS enabled

This is due to UBSAN generating signed-overflow-UB warnings where it
should not. Prior to GCC-8 UBSAN ignored -fwrapv (which the kernel
uses through -fno-strict-overflow).

Make the functions use 'unsigned long' throughout.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: luto@kernel.org
Link: http://lkml.kernel.org/r/20190424072208.754094071@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
lib/strncpy_from_user.c
lib/strnlen_user.c