From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 039B237DE97; Tue, 21 Jul 2026 18:20:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784658012; cv=none; b=HhrmSVK8UYPmACCN5bnEv4rTqgvyMOKoZ1VMXV3RMGB1iiiQUp61Fx0SY2fiXsmzC/hlQ4pAaF0pdBd8bm4kn//M9k4WHJhZtA6BioTOm3x6qzZGPOHqqSuY0NnIWBHEqbNOqOVCPQzEKPBce6yPLEgrh4WRiTMtbRPwViMfaY4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784658012; c=relaxed/simple; bh=CyswDC8neBRnbKf/uM06kJ4YEZAlljIP9vHagu9pHGs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iJ6WxNAxKTXgfNarJUnikC6uO1toia3XrNFs6wVX1+ABXtgVa+voDTAydrDixETzvyN84E0hEUC0p444Sqv15O6kNxmT2T7XnkwvZxOCaelSrpg7z4ZZq1MPK4jgEHydMPppukIZy4w6VYUlB0u4ghLDyqCUJnyErhMNtYPeu0g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=m/RgZkOU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="m/RgZkOU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 693321F000E9; Tue, 21 Jul 2026 18:20:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784658010; bh=XRVLCsajYzR7ooJvvr1dz88Gtn+2px0Qu1MEY6raOew=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=m/RgZkOUpiwWI4Zaay90j4B/0sMf7s+FzJO8QjBXsy8njyTL8GopcD2yw0RyLTu8G es2dxpByn6BI4oiwAcn7pSS6MeLvVBWjt70rI3+6ADykRrpYHh5RwxNpzGqmBO+dJt 0JB8rVyKZRgOt19VGommaNa6tPhwX5xF0MDGXKnE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sechang Lim , "Masami Hiramatsu (Google)" , Sasha Levin Subject: [PATCH 6.18 0983/1611] tracing/fprobe: Fix NULL pointer dereference in fprobe_fgraph_entry() Date: Tue, 21 Jul 2026 17:18:19 +0200 Message-ID: <20260721152537.502969256@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sechang Lim [ Upstream commit 367c49d6e283c17b56a31e7a8d964a079244264c ] fprobe_fgraph_entry() sizes a shadow-stack reservation in one walk of the per-ip fprobe list and fills it in a second walk, both under rcu_read_lock() only. A fprobe registered on an already-live ip can become visible between the two walks, so the fill walk processes an exit_handler the sizing walk did not count and used runs past reserved_words. If the sizing walk counted nothing, fgraph_data is NULL and the first write_fprobe_header() faults: Oops: general protection fault, probably for non-canonical address ... KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:fprobe_fgraph_entry+0xa38/0xf10 kernel/trace/fprobe.c:167 Call Trace: function_graph_enter_regs+0x44c/0xa10 kernel/trace/fgraph.c:677 ftrace_graph_func+0xc5/0x140 arch/x86/kernel/ftrace.c:671 __kernel_text_address+0x9/0x40 kernel/extable.c:78 arch_stack_walk+0x117/0x170 arch/x86/kernel/stacktrace.c:26 kmem_cache_free+0x188/0x580 mm/slub.c:6378 tcp_data_queue+0x18d/0x6550 net/ipv4/tcp_input.c:5590 [...] The list cannot be frozen across the two walks, so skip a node that does not fit the reservation and count it as missed. Link: https://lore.kernel.org/all/20260619184425.3824774-1-rhkrqnwk98@gmail.com/ Fixes: 4346ba160409 ("fprobe: Rewrite fprobe on function-graph tracer") Signed-off-by: Sechang Lim Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Sasha Levin --- kernel/trace/fprobe.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index b9346f4efa6dc1..01f98f8a86e606 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -474,6 +474,16 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops continue; data_size = fp->entry_data_size; + /* + * The list may have grown since it was sized, so this node + * may not fit. Skip it as missed rather than overrun the + * reservation. + */ + if (fp->exit_handler && + used + FPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(data_size) > reserved_words) { + fp->nmissed++; + continue; + } if (data_size && fp->exit_handler) data = fgraph_data + used + FPROBE_HEADER_SIZE_IN_LONG; else -- 2.53.0