From nobody Sun Feb 8 21:33:01 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E4B672E62C; Sun, 6 Apr 2025 18:42:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743964946; cv=none; b=EZiaFQedTNWqpk4EvDDfInWrHMCW/b73DBlHzJDgyRLIWMZQBDmFJAKlWYfWJSiN3BJoIYfIxJtOEZVLhquai/EAKw84d2eDCBRLLUvvQaBuU3OdTQBztSzvGU8bsacPv5gdxiPDYcii0ZRvnRYloSPf3lmVgU2FF5Xuq72C670= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743964946; c=relaxed/simple; bh=z7IyGIugvU25wFZxIBRUUQmzKyoNvqA3uTExL14tq/Q=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=PVebdhILyKzP0RK6cZFFnnlOYt24gMoFRI5qBk/rM0fGfLuxDTlklaCPyosBJajnmC3W4Pdyg7x/4ZFhegAg0oN+WkSDsX3r1f7MpGLWOmJMWrxWAUNX4OMGNBpF1j1PhLQx6Y2QELXq3SmhpziGJ0rtsi23XjkOh0j8B6k1l5A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=kcp+bOoR; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=uhtDH5k9; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="kcp+bOoR"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="uhtDH5k9" Date: Sun, 06 Apr 2025 18:42:22 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1743964943; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dmj+zo6C3P/pSg/s1RkYC7RWN47ojlSz5x1oHCbh38s=; b=kcp+bOoRh1/W1Eg1W3Qf/Nv2mI0opUBOrg7J7S3/VjqSnK6kEvxQdzjRz8IaWMe9DhFnnR tyZg3OEiTtoQixTE8gZp2r2uLvHZSrx6jdANDMLt9ZiPjvyZ6vxedTAuD41kruyZ9abMcE GOhDT2oJbtewaeFvH3prZc3B+vPd6zS7u6b+N+9uOketNzj06/peW7D3U5OoBcxsjbf1aj 643D7qgR02V+NTHJIhsmTLvgXmQIWMEXsrb3GnwfiZERPqrG+byhVT85nvaraVxEairy50 z4orXIckL7ild6mKIHKLQSiP+RmsjmsA3ld1ZTxfyBQnIC1c3lWXojnYhxPZOQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1743964943; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dmj+zo6C3P/pSg/s1RkYC7RWN47ojlSz5x1oHCbh38s=; b=uhtDH5k9RSF+A2+oeAMD0xlNQrUBl94qDXkqNWQdnRvlDLrs8mcYtGOdAzFASsgjDsAUmu eX/LCRyUzFfjxGBw== From: "tip-bot2 for Gabriel Shahrouzi" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/urgent] perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init Cc: syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com, Gabriel Shahrouzi , Ingo Molnar , Peter Zijlstra , Ravi Bangoria , Kan Liang , Oleg Nesterov , Alexander Shishkin , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250405203036.582721-1-gshahrouzi@gmail.com> References: <20250405203036.582721-1-gshahrouzi@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174396494203.31282.1919457781258540750.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/urgent branch of tip: Commit-ID: 0ba3a4ab76fd3367b9cb680cad70182c896c795c Gitweb: https://git.kernel.org/tip/0ba3a4ab76fd3367b9cb680cad70182c8= 96c795c Author: Gabriel Shahrouzi AuthorDate: Sat, 05 Apr 2025 16:30:36 -04:00 Committer: Ingo Molnar CommitterDate: Sun, 06 Apr 2025 20:30:28 +02:00 perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init Move the get_ctx(child_ctx) call and the child_event->ctx assignment to occur immediately after the child event is allocated. Ensure that child_event->ctx is non-NULL before any subsequent error path within inherit_event calls free_event(), satisfying the assumptions of the cleanup code. Details: There's no clear Fixes tag, because this bug is a side-effect of multiple interacting commits over time (up to 15 years old), not a single regression. The code initially incremented refcount then assigned context immediately after the child_event was created. Later, an early validity check for child_event was added before the refcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was added, assuming event->ctx is valid if the pmu_ctx is valid. The problem is that the WARN_ON_ONCE() could trigger after the initial check passed but before child_event->ctx was assigned, violating its precondition. The solution is to assign child_event->ctx right after its initial validation. This ensures the context exists for any subsequent checks or cleanup routines, resolving the WARN_ON_ONCE(). To resolve it, defer the refcount update and child_event->ctx assignment directly after child_event->pmu_ctx is set but before checking if the parent event is orphaned. The cleanup routine depends on event->pmu_ctx being non-NULL before it verifies event->ctx is non-NULL. This also maintains the author's original intent of passing in child_ctx to find_get_pmu_context before its refcount/assignment. [ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ] Reported-by: syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com Signed-off-by: Gabriel Shahrouzi Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Cc: Ravi Bangoria Cc: Kan Liang Cc: Oleg Nesterov Cc: Alexander Shishkin Link: https://lore.kernel.org/r/20250405203036.582721-1-gshahrouzi@gmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dff3aa851d46ab82953a3 --- kernel/events/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 128db74..9af9726 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -14016,6 +14016,9 @@ inherit_event(struct perf_event *parent_event, if (IS_ERR(child_event)) return child_event; =20 + get_ctx(child_ctx); + child_event->ctx =3D child_ctx; + pmu_ctx =3D find_get_pmu_context(child_event->pmu, child_ctx, child_event= ); if (IS_ERR(pmu_ctx)) { free_event(child_event); @@ -14037,8 +14040,6 @@ inherit_event(struct perf_event *parent_event, return NULL; } =20 - get_ctx(child_ctx); - /* * Make the child state follow the state of the parent event, * not its attr.disabled bit. We hold the parent's mutex, @@ -14059,7 +14060,6 @@ inherit_event(struct perf_event *parent_event, local64_set(&hwc->period_left, sample_period); } =20 - child_event->ctx =3D child_ctx; child_event->overflow_handler =3D parent_event->overflow_handler; child_event->overflow_handler_context =3D parent_event->overflow_handler_context;