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 EEEEC350D57; Tue, 6 Jan 2026 17:22:25 +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=1767720146; cv=none; b=CD2TF1J+JyxM0+73IFWUcjJJKtsw5I3zQxc76hIGOLvWFssNUlum6YYVy8i9w8L6UFVLwo+YvjvUXPWrbpNzKCXmmAdcIDCvS9/gAFqb5quySCSo4W1M0Q8KDimw1+sZQxM7kLab0PpEqUkJTfWkAp8QXWr5zWAVFswyXBNSBeY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767720146; c=relaxed/simple; bh=5RG7QYKMOP2EROVwI1Tn9QlCP3GvUgTym/P/XCbvM9U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YGyjltq940LzU+SgV5OwsohSBw2PAzYfQEzglTwu1PsCNGnU54wEoZy7WAPUNDv4ebVwZ8OL29B0dfUBoafowJFb+tzsORQwrkokp/0aou48XLtehAGNLKlh6Fbc/v/tK5QC1MOENRthrefieYOg3bKor33mI6t/uE6lTMn17XE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gzu/6ezG; 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="gzu/6ezG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BE6DC116C6; Tue, 6 Jan 2026 17:22:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767720145; bh=5RG7QYKMOP2EROVwI1Tn9QlCP3GvUgTym/P/XCbvM9U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gzu/6ezGeW+v80Z4cq6nO3VsaT7x4DDkHzIujfAHxyxzvBH8SOqKNS5iTeNEC2DOe 0GoA/K3tpecoNL1NKCqc1eBaz3MxMCMQ1KOkbOGZY/5Rgss38C7RfN1IJ+IylS/JKx rq+IJF2Jv1Y20W3Jm+JhGWRHLaV9PNIbxlOhljIo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gregory CLEMENT , Thomas Bogendoerfer , Sasha Levin Subject: [PATCH 6.12 148/567] MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits Date: Tue, 6 Jan 2026 17:58:50 +0100 Message-ID: <20260106170456.800950888@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170451.332875001@linuxfoundation.org> References: <20260106170451.332875001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gregory CLEMENT [ Upstream commit 36dac9a3dda1f2bae343191bc16b910c603cac25 ] Since commit e424054000878 ("MIPS: Tracing: Reduce the overhead of dynamic Function Tracer"), the macro UASM_i_LA_mostly has been used, and this macro can generate more than 2 instructions. At the same time, the code in ftrace assumes that no more than 2 instructions can be generated, which is why it stores them in an int[2] array. However, as previously noted, the macro UASM_i_LA_mostly (and now UASM_i_LA) causes a buffer overflow when _mcount is beyond 32 bits. This leads to corruption of the variables located in the __read_mostly section. This corruption was observed because the variable __cpu_primary_thread_mask was corrupted, causing a hang very early during boot. This fix prevents the corruption by avoiding the generation of instructions if they could exceed 2 instructions in length. Fortunately, insn_la_mcount is only used if the instrumented code is located outside the kernel code section, so dynamic ftrace can still be used, albeit in a more limited scope. This is still preferable to corrupting memory and/or crashing the kernel. Signed-off-by: Gregory CLEMENT Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin --- arch/mips/kernel/ftrace.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c index f39e85fd58fa..b15615b28569 100644 --- a/arch/mips/kernel/ftrace.c +++ b/arch/mips/kernel/ftrace.c @@ -54,10 +54,20 @@ static inline void ftrace_dyn_arch_init_insns(void) u32 *buf; unsigned int v1; - /* la v1, _mcount */ - v1 = 3; - buf = (u32 *)&insn_la_mcount[0]; - UASM_i_LA(&buf, v1, MCOUNT_ADDR); + /* If we are not in compat space, the number of generated + * instructions will exceed the maximum expected limit of 2. + * To prevent buffer overflow, we avoid generating them. + * insn_la_mcount will not be used later in ftrace_make_call. + */ + if (uasm_in_compat_space_p(MCOUNT_ADDR)) { + /* la v1, _mcount */ + v1 = 3; + buf = (u32 *)&insn_la_mcount[0]; + UASM_i_LA(&buf, v1, MCOUNT_ADDR); + } else { + pr_warn("ftrace: mcount address beyond 32 bits is not supported (%lX)\n", + MCOUNT_ADDR); + } /* jal (ftrace_caller + 8), jump over the first two instruction */ buf = (u32 *)&insn_jal_ftrace_caller; @@ -189,6 +199,13 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) unsigned int new; unsigned long ip = rec->ip; + /* When the code to patch does not belong to the kernel code + * space, we must use insn_la_mcount. However, if MCOUNT_ADDR + * is not in compat space, insn_la_mcount is not usable. + */ + if (!core_kernel_text(ip) && !uasm_in_compat_space_p(MCOUNT_ADDR)) + return -EFAULT; + new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0]; #ifdef CONFIG_64BIT -- 2.51.0