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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483bd75df90sm120961275e9.14.2026.02.25.21.26.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Feb 2026 21:26:46 -0800 (PST) From: David Carlier To: Tejun Heo , David Vernet Cc: linux-kernel@vger.kernel.org, David Carlier Subject: [PATCH 2/2] sched_ext: Fix TOCTOU on p->scx.dsq in scx_dump_task() Date: Thu, 26 Feb 2026 05:26:40 +0000 Message-ID: <20260226052640.7191-2-devnexen@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260226052640.7191-1-devnexen@gmail.com> References: <20260226052640.7191-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit p->scx.dsq is checked for NULL then dereferenced without synchronization. Another CPU can NULL the pointer between the check and the use. Use READ_ONCE() to capture the pointer into a local variable before dereferencing. Signed-off-by: David Carlier --- kernel/sched/ext.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index eb539b671c49..444398f3686a 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4597,9 +4597,11 @@ static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx, unsigned long ops_state = atomic_long_read(&p->scx.ops_state); unsigned int bt_len = 0; - if (p->scx.dsq) + struct scx_dispatch_q *dsq = READ_ONCE(p->scx.dsq); + + if (dsq) scnprintf(dsq_id_buf, sizeof(dsq_id_buf), "0x%llx", - (unsigned long long)p->scx.dsq->id); + (unsigned long long)dsq->id); dump_newline(s); dump_line(s, " %c%c %s[%d] %+ldms", -- 2.51.0