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Wed, 11 Jun 2025 12:15:09 -0700 (PDT) Received: from pc636 ([2001:9b1:d5a0:a500::800]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-55384f3deeesm1408927e87.62.2025.06.11.12.15.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Jun 2025 12:15:09 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 11 Jun 2025 21:15:07 +0200 To: syzbot Cc: akpm@linux-foundation.org, josh@joshtriplett.org, kent.overstreet@linux.dev, linux-bcachefs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paulmck@kernel.org, rcu@vger.kernel.org, syzkaller-bugs@googlegroups.com, urezki@gmail.com Subject: Re: [syzbot] [bcachefs?] [rcu?] BUG: unable to handle kernel NULL pointer dereference in rcu_core (3) Message-ID: References: <6849c49b.a00a0220.1eb5f5.00f2.GAE@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6849c49b.a00a0220.1eb5f5.00f2.GAE@google.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2C3DB2000E X-Stat-Signature: 8gwm8yipi85qhhmom1swig37d4ks1a4u X-Rspam-User: X-HE-Tag: 1749669311-427005 X-HE-Meta: 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 Jm5P2PTy 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jun 11, 2025 at 11:02:03AM -0700, syzbot wrote: > Hello, > > syzbot tried to test the proposed patch but the build/boot failed: > > failed to apply patch: > checking file kernel/rcu/tree.c > patch: **** unexpected end of file in patch > > > > Tested on: > > commit: aef17cb3 Revert "mm/damon/Kconfig: enable CONFIG_DAMON.. > git tree: upstream > kernel config: https://syzkaller.appspot.com/x/.config?x=523d3ff8e053340a > dashboard link: https://syzkaller.appspot.com/bug?extid=80e5d6f453f14a53383a > compiler: > patch: https://syzkaller.appspot.com/x/patch.diff?x=17de99d4580000 > #syz test diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e8a4b720d7d2..14d4499c6fc3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3072,6 +3072,10 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); + /* Avoid NULL dereference if callback is NULL. */ + if (WARN_ON_ONCE(!func)) + return; + if (debug_rcu_head_queue(head)) { /* * Probable double call_rcu(), so leak the callback.