From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8C228155A4E; Tue, 29 Apr 2025 18:17:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745950638; cv=none; b=ehCxwlBWl/LXsBqqZfhRbMQFjnzKvIzj6/f7/6rc/BfsBMRj+XdghdQf+15kcWUTpF1Dw0SS8PXj0ETiRHy4BINaPfCcTpx6Kpm1noILF7NwR4yauaN1Gh/FNJ5Ja0QIIzD+2f+pfLhQOSbDK65M+GJi1kOkjkQAe7RavpADHUs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745950638; c=relaxed/simple; bh=hfiFDYG5oUflXYIILtfYK2IwRwCi4sQe1P+jEL5bCU0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Rg9ZUC1bQlld8Uh0f6GX14Dprk1HDbiSWFxsQl4GwBD1Fp1vjEuGLHqKCB/lXd0Ei3199ltmGj9l5kSDswr8v/xuTzle4ZjeBHq4P3R0A2HMjyO41f7NO2ybmtP4PlgdZRofdeLUuJUfDQoG+URk2fuOxrITOiqTb/Ge15HXymI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=jVc2IUgS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="jVc2IUgS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E448C4CEE3; Tue, 29 Apr 2025 18:17:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745950637; bh=hfiFDYG5oUflXYIILtfYK2IwRwCi4sQe1P+jEL5bCU0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jVc2IUgSden92HkDWDDrLVNS4RCAK+MGADvStWJtU28Nw9Uqx+KsUG9eyPRkWasf0 w9NmueIZJsycL9Og3k5/HzHuEaCsSqTOFfROO918VrJAe23Ex63bMliluYcN3e2WUF 7pYg9ruhgiotH8LaszDWRZwKd4TZoFTBqdeqm+p4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com, Gabriel Shahrouzi , Ingo Molnar , Peter Zijlstra , Ravi Bangoria , Kan Liang , Oleg Nesterov , Alexander Shishkin , Sasha Levin Subject: [PATCH 6.6 157/204] perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init Date: Tue, 29 Apr 2025 18:44:05 +0200 Message-ID: <20250429161105.839044339@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250429161059.396852607@linuxfoundation.org> References: <20250429161059.396852607@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gabriel Shahrouzi [ Upstream commit 0ba3a4ab76fd3367b9cb680cad70182c896c795c ] 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=ff3aa851d46ab82953a3 Signed-off-by: Sasha Levin --- 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 b710976fb01b1..987807b1040ae 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -13419,6 +13419,9 @@ inherit_event(struct perf_event *parent_event, if (IS_ERR(child_event)) return child_event; + get_ctx(child_ctx); + child_event->ctx = child_ctx; + pmu_ctx = find_get_pmu_context(child_event->pmu, child_ctx, child_event); if (IS_ERR(pmu_ctx)) { free_event(child_event); @@ -13441,8 +13444,6 @@ inherit_event(struct perf_event *parent_event, return NULL; } - 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, @@ -13463,7 +13464,6 @@ inherit_event(struct perf_event *parent_event, local64_set(&hwc->period_left, sample_period); } - child_event->ctx = child_ctx; child_event->overflow_handler = parent_event->overflow_handler; child_event->overflow_handler_context = parent_event->overflow_handler_context; -- 2.39.5