From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 07/35] mm/gup: fix null pointer dereference detected by coverity Date: Fri, 10 Apr 2020 14:32:35 -0700 Message-ID: <20200410213235.M6eTaELL2%akpm@linux-foundation.org> References: <20200410143047.bf34a933ce1affdc042c7c80@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:46428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726582AbgDJVcf (ORCPT ); Fri, 10 Apr 2020 17:32:35 -0400 In-Reply-To: <20200410143047.bf34a933ce1affdc042c7c80@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, ira.weiny@intel.com, linux-mm@kvack.org, miles.chen@mediatek.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org From: Miles Chen Subject: mm/gup: fix null pointer dereference detected by coverity In fixup_user_fault(), it is possible that unlocked is NULL, so we should test unlocked before using it. For example, in arch/arc/kernel/process.c, NULL is passed to fixup_user_fault(). SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) { ... ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr, FAULT_FLAG_WRITE, NULL); ... } Link: http://lkml.kernel.org/r/20200407095107.1988-1-miles.chen@mediatek.com Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock") Signed-off-by: Miles Chen Reviewed-by: Ira Weiny Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton --- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/gup.c~mm-gup-fix-null-pointer-dereference-detected-by-coverity +++ a/mm/gup.c @@ -1231,7 +1231,8 @@ retry: if (ret & VM_FAULT_RETRY) { down_read(&mm->mmap_sem); if (!(fault_flags & FAULT_FLAG_TRIED)) { - *unlocked = true; + if (unlocked) + *unlocked = true; fault_flags |= FAULT_FLAG_TRIED; goto retry; } _