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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6fb35c4cf21sm12320366d6.87.2025.06.12.10.33.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jun 2025 10:33:43 -0700 (PDT) Received: from phl-compute-01.internal (phl-compute-01.phl.internal [10.202.2.41]) by mailfauth.phl.internal (Postfix) with ESMTP id B5A051200043; Thu, 12 Jun 2025 13:33:42 -0400 (EDT) Received: from phl-imap-16 ([10.202.2.88]) by phl-compute-01.internal (MEProxy); Thu, 12 Jun 2025 13:33:42 -0400 X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtddugdduheeikecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpggftfghnshhusghstghrihgsvgdp uffrtefokffrpgfnqfghnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivg hnthhsucdlqddutddtmdenucfjughrpefoggffhffvvefkjghfufgtgfesthhqredtredt jeenucfhrhhomhepfdeuohhquhhnucfhvghnghdfuceosghoqhhunhdrfhgvnhhgsehgmh grihhlrdgtohhmqeenucggtffrrghtthgvrhhnpeeileeuiefffeffiefgleehgefgueeu tddvjedvjeetveduffetfeffgfektdeutdenucevlhhushhtvghrufhiiigvpedtnecurf grrhgrmhepmhgrihhlfhhrohhmpegsohhquhhnodhmvghsmhhtphgruhhthhhpvghrshho nhgrlhhithihqdeiledvgeehtdeigedqudejjeekheehhedvqdgsohhquhhnrdhfvghngh eppehgmhgrihhlrdgtohhmsehfihigmhgvrdhnrghmvgdpnhgspghrtghpthhtohepledp mhhouggvpehsmhhtphhouhhtpdhrtghpthhtohepnhgvvghrrghjrdhuphgrughhhigrhi esrghmugdrtghomhdprhgtphhtthhopehurhgviihkihesghhmrghilhdrtghomhdprhgt phhtthhopehjohgvlhesjhhovghlfhgvrhhnrghnuggvshdrohhrghdprhgtphhtthhope hfrhgvuggvrhhitgeskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepphgruhhlmhgtkhes khgvrhhnvghlrdhorhhgpdhrtghpthhtohepjhhovghlrghgnhgvlhhfsehnvhhiughirg drtghomhdprhgtphhtthhopeholhgvkhhsihihrdgrvhhrrghmtghhvghnkhhosehsohhn hidrtghomhdprhgtphhtthhopehlihhnuhigqdhkvghrnhgvlhesvhhgvghrrdhkvghrnh gvlhdrohhrghdprhgtphhtthhopehrtghusehvghgvrhdrkhgvrhhnvghlrdhorhhg X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mailuser.phl.internal (Postfix, from userid 501) id 8CF312CC0081; Thu, 12 Jun 2025 13:33:42 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Tf837c207727b83ac Date: Thu, 12 Jun 2025 10:33:22 -0700 From: "Boqun Feng" To: "Joel Fernandes" , "Uladzislau Rezki (Sony)" , "Paul E. McKenney" , "Joel Fernandes" , "Neeraj Upadhyay" Cc: RCU , LKML , "Frederic Weisbecker" , "Oleksiy Avramchenko" Message-Id: In-Reply-To: <0caf7054-140e-4b6c-abd4-2ec2ebe79b2c@app.fastmail.com> References: <20250610173450.107293-1-urezki@gmail.com> <4bc63cf3-29a4-4a64-be65-30f7bd55e31c@nvidia.com> <0caf7054-140e-4b6c-abd4-2ec2ebe79b2c@app.fastmail.com> Subject: Re: [PATCH 1/3] rcu: Return early if callback is not specified Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Thu, Jun 12, 2025, at 10:30 AM, Boqun Feng wrote: > On Tue, Jun 10, 2025, at 12:33 PM, Joel Fernandes wrote: >> On 6/10/2025 1:34 PM, Uladzislau Rezki (Sony) wrote: >>> Currently the call_rcu() API does not check whether a callback >>> pointer is NULL. If NULL is passed, rcu_core() will try to invoke >>> it, resulting in NULL pointer dereference and a kernel crash. >>>=20 >>> To prevent this and improve debuggability, this patch adds a check >>> for NULL and emits a kernel stack trace to help identify a faulty >>> caller. >>>=20 >>> Signed-off-by: Uladzislau Rezki (Sony) >> >> Reviewed-by: Joel Fernandes >> > > Reviewed-by: Boqun Feng > (Accidentally sent from another email account, FWIW, this is Boqun Feng and I approve this message, sorry couldn=E2=80=99t resist :)) Regards, Boqun >> I will add this first one (only this one since we're discussing the o= thers) to a >> new rcu/fixes-for-6.16 branch, but let me know if any objections. >> > > Not sure it=E2=80=99s urgent enough given the current evidence. > > Regards, > Boqun > >> Will push that branch out during -rc2 or -rc3 after sufficient testin= g. >> >> thanks, >> >> - Joel >> >>> --- >>> kernel/rcu/tree.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>>=20 >>> 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)); >>> =20 >>> + /* 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.