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 79DC2374E60; Sat, 17 Oct 2026 17:32:42 +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=1792258363; cv=none; b=VB7G8uo5WS0WfMAOJ/AwvzvnwsRSZCAVNE999uN0/mANUXLtq1v/nWVoVX8TD2idlQa+nvgKskrfCJGxjdPFo/6nn5aykN/DCVDy1wvQCtQb+LonmtSFEFkpxHXSJLIL0S2jqXGCaivBj49YpOp280AvgKn/bgZsIthXxXoKID8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792258363; c=relaxed/simple; bh=OxURTCZN75SOXj0t70hlH872tqAf7GBYDgOzTmDa5pg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MbRYOSTANLMdX1Nzr7iLYkRma2YTeZE5xkxndy/QC55nwIbk/lUN4KCcKFOaoD9Gbp+Q3lNRakmzSubACQYv0HqApX72rC+kzhBQ0f6xeOUoabaJKRZjuKNZnyLGfCVv0knSiohexjVnnSdj0hJAwLn+NrfDDFTZzVdveQpOIgw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=n+6IFLaN; 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="n+6IFLaN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFAA81F000C4; Sat, 17 Oct 2026 17:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792258362; bh=Fu5neLRiaLjWc1sk2knjD9tIJ65t+iDDKFmj6npeJR0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=n+6IFLaN0OpJp6Ydazl+8m6pWjMXWriozqiVimu7mKbci7NnQDfuMe3YguzMiBMf0 jLaOThVfaXURKPJJJiNcgboAtnm7727ZamMKkrekfECDDDXj3i3XZfIfDBev57ZnN6 oqVxEG74Ym8563vwsEslmlC9qKcao4KQXC/EkHkg= 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 6.6 0842/1674] MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits Date: Sat, 17 Oct 2026 17:51:54 +0200 Message-ID: <20261017160452.741871746@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@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 6.6-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 f39e85fd58fa9..b15615b285690 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 -- 2.53.0