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 8E0D415AADE; Thu, 29 Feb 2024 20:39:52 +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=1709239192; cv=none; b=hkZlgWrF1SIu0TlJ4uyhHRfnH25cLAsXt7RAUgNjzWFKr85SoJn8WIgbwjPMMBqPkQWazliXOcRgdcncXsbbNnbwaclKw0lv0ZgPsOR/xPz9WIfZT/RckU3pyOgNDLYO9fzT3fvY23ECipDzNLgVZ2/iikx6B+xcI0/eeS3cOfQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709239192; c=relaxed/simple; bh=Vo3k/UgoRrmyUGzlldwCCqinbenvGMIr4yM+BJI4MQQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SaD9TVmj1se/v/MspJNKyVR4jiELo524t4INwkHhBbNMWxqXF8imONPb3zuDv80MuUi589NCIeoUA5WBqHk0sQ3H+oSkcA7N81X7kiwvCq0XY98riiiEYfsrCt7LYdnscvHrTcCQoVujZ8HYY7LLzQMguUxrwWS7g2RnPuZz7/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tDXjuP66; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tDXjuP66" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58CA1C433B1; Thu, 29 Feb 2024 20:39:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709239192; bh=Vo3k/UgoRrmyUGzlldwCCqinbenvGMIr4yM+BJI4MQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tDXjuP660O0g7DUB7/MSdlfNaB0OMbNWWgBSQBSq8Fiboilan1jLEhRMJXZ5rUswB MPUhDpOrUd9jBK+TOjBB1KjkLyAEF80tYGS597+3uJaKcteJ3PYQzPV1YATD8pAObY MLrIvB68so0GRGn+EiHktcOKgM1sKQm15aEZum4AoMm3FwJg63OoROqpWoLoyz9oFl WdAnlZgg/8T69TqDmvwacEeQ/PE3qsS85y+p7isI74I352m3a+YP34Q6JGOWcwsavI 0OenL3lWhHLqhffP9Xskmc3sVls/2DBwd/19EHOXhyDqlrVN/ISyxilAKOMAHewMYQ RyY6HNpJbATeQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hou Tao , Thomas Gleixner , syzbot+72aa0161922eba61b50e@syzkaller.appspotmail.com, xingwei lee , Sohil Mehta , Alexei Starovoitov , Sasha Levin , dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 6.6 08/22] x86/mm: Disallow vsyscall page read for copy_from_kernel_nofault() Date: Thu, 29 Feb 2024 15:39:01 -0500 Message-ID: <20240229203933.2861006-8-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240229203933.2861006-1-sashal@kernel.org> References: <20240229203933.2861006-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.18 Content-Transfer-Encoding: 8bit From: Hou Tao [ Upstream commit 32019c659ecfe1d92e3bf9fcdfbb11a7c70acd58 ] When trying to use copy_from_kernel_nofault() to read vsyscall page through a bpf program, the following oops was reported: BUG: unable to handle page fault for address: ffffffffff600000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 3231067 P4D 3231067 PUD 3233067 PMD 3235067 PTE 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 1 PID: 20390 Comm: test_progs ...... 6.7.0+ #58 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ...... RIP: 0010:copy_from_kernel_nofault+0x6f/0x110 ...... Call Trace: ? copy_from_kernel_nofault+0x6f/0x110 bpf_probe_read_kernel+0x1d/0x50 bpf_prog_2061065e56845f08_do_probe_read+0x51/0x8d trace_call_bpf+0xc5/0x1c0 perf_call_bpf_enter.isra.0+0x69/0xb0 perf_syscall_enter+0x13e/0x200 syscall_trace_enter+0x188/0x1c0 do_syscall_64+0xb5/0xe0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 ...... ---[ end trace 0000000000000000 ]--- The oops is triggered when: 1) A bpf program uses bpf_probe_read_kernel() to read from the vsyscall page and invokes copy_from_kernel_nofault() which in turn calls __get_user_asm(). 2) Because the vsyscall page address is not readable from kernel space, a page fault exception is triggered accordingly. 3) handle_page_fault() considers the vsyscall page address as a user space address instead of a kernel space address. This results in the fix-up setup by bpf not being applied and a page_fault_oops() is invoked due to SMAP. Considering handle_page_fault() has already considered the vsyscall page address as a userspace address, fix the problem by disallowing vsyscall page read for copy_from_kernel_nofault(). Originally-by: Thomas Gleixner Reported-by: syzbot+72aa0161922eba61b50e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/bpf/CAG48ez06TZft=ATH1qh2c5mpS5BT8UakwNkzi6nvK5_djC-4Nw@mail.gmail.com Reported-by: xingwei lee Closes: https://lore.kernel.org/bpf/CABOYnLynjBoFZOf3Z4BhaZkc5hx_kHfsjiW+UWLoB=w33LvScw@mail.gmail.com Signed-off-by: Hou Tao Reviewed-by: Sohil Mehta Acked-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240202103935.3154011-3-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- arch/x86/mm/maccess.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/mm/maccess.c b/arch/x86/mm/maccess.c index 6993f026adec9..42115ac079cfe 100644 --- a/arch/x86/mm/maccess.c +++ b/arch/x86/mm/maccess.c @@ -3,6 +3,8 @@ #include #include +#include + #ifdef CONFIG_X86_64 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) { @@ -15,6 +17,14 @@ bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) if (vaddr < TASK_SIZE_MAX + PAGE_SIZE) return false; + /* + * Reading from the vsyscall page may cause an unhandled fault in + * certain cases. Though it is at an address above TASK_SIZE_MAX, it is + * usually considered as a user space address. + */ + if (is_vsyscall_vaddr(vaddr)) + return false; + /* * Allow everything during early boot before 'x86_virt_bits' * is initialized. Needed for instruction decoding in early -- 2.43.0