linux-kernel - [PATCH] powerpc/mm: avoid null pointer dereference in flush_tlb

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Message-Id: <1608880271-2294955-1-git-send-email-bodefang@126.com>
Date:   Fri, 25 Dec 2020 15:11:11 +0800
From:   Defang Bo <bodefang@....com>
To:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org
Cc:     akpm@...ux-foundation.org, rppt@...nel.org,
        christophe.leroy@...roup.eu, penberg@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Defang Bo <bodefang@....com>
Subject: [PATCH] powerpc/mm: avoid null pointer dereference in flush_tlb_mm

Similar to commit<0dc294f7>, there should be a check for 'mm' to prevent Null pointer dereference in case of 'mm' argument was legitimately passed.

Signed-off-by: Defang Bo <bodefang@....com>
---
 arch/powerpc/mm/nohash/tlb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/mm/nohash/tlb.c b/arch/powerpc/mm/nohash/tlb.c
index 5872f69..09796c9 100644
--- a/arch/powerpc/mm/nohash/tlb.c
+++ b/arch/powerpc/mm/nohash/tlb.c
@@ -268,6 +268,9 @@ void flush_tlb_mm(struct mm_struct *mm)
 {
 	unsigned int pid;
 
+	if (unlikely(!mm))
+		return;
+
 	preempt_disable();
 	pid = mm->context.id;
 	if (unlikely(pid == MMU_NO_CONTEXT))
-- 
2.7.4