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Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:35310) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1i3hGR-00079z-DU; Fri, 30 Aug 2019 14:48:31 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1i3hGP-0000BO-2I; Fri, 30 Aug 2019 14:48:29 +0100 Date: Fri, 30 Aug 2019 14:48:29 +0100 From: Russell King - ARM Linux admin To: Jing Xiangfeng Subject: Re: [PATCH] arm: fix page faults in do_alignment Message-ID: <20190830134828.GC13294@shell.armlinux.org.uk> References: <1567171877-101949-1-git-send-email-jingxiangfeng@huawei.com> <20190830133522.GZ13294@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190830133522.GZ13294@shell.armlinux.org.uk> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190830_064911_899256_2EE2A716 X-CRM114-Status: GOOD ( 22.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kstewart@linuxfoundation.org, gustavo@embeddedor.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ebiederm@xmission.com, sakari.ailus@linux.intel.com, bhelgaas@google.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Please fix your email. jingxiangfeng@huawei.com host mx7.huawei.com [168.195.93.46] SMTP error from remote mail server after pipelined DATA: 554 5.7.1 spf check result is none SPF is *not* required for email. If you wish to impose such restrictions on email, then I reserve the right to ignore your patches until this issue is resolved! ;) On Fri, Aug 30, 2019 at 02:35:22PM +0100, Russell King - ARM Linux admin wrote: > On Fri, Aug 30, 2019 at 09:31:17PM +0800, Jing Xiangfeng wrote: > > The function do_alignment can handle misaligned address for user and > > kernel space. If it is a userspace access, do_alignment may fail on > > a low-memory situation, because page faults are disabled in > > probe_kernel_address. > > > > Fix this by using __copy_from_user stead of probe_kernel_address. > > > > Fixes: b255188 ("ARM: fix scheduling while atomic warning in alignment handling code") > > Signed-off-by: Jing Xiangfeng > > NAK. > > The "scheduling while atomic warning in alignment handling code" is > caused by fixing up the page fault while trying to handle the > mis-alignment fault generated from an instruction in atomic context. > > Your patch re-introduces that bug. > > > --- > > arch/arm/mm/alignment.c | 16 +++++++++++++--- > > 1 file changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c > > index 04b3643..2ccabd3 100644 > > --- a/arch/arm/mm/alignment.c > > +++ b/arch/arm/mm/alignment.c > > @@ -774,6 +774,7 @@ static ssize_t alignment_proc_write(struct file *file, const char __user *buffer > > unsigned long instr = 0, instrptr; > > int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs); > > unsigned int type; > > + mm_segment_t fs; > > unsigned int fault; > > u16 tinstr = 0; > > int isize = 4; > > @@ -784,16 +785,22 @@ static ssize_t alignment_proc_write(struct file *file, const char __user *buffer > > > > instrptr = instruction_pointer(regs); > > > > + fs = get_fs(); > > + set_fs(KERNEL_DS); > > if (thumb_mode(regs)) { > > u16 *ptr = (u16 *)(instrptr & ~1); > > - fault = probe_kernel_address(ptr, tinstr); > > + fault = __copy_from_user(tinstr, > > + (__force const void __user *)ptr, > > + sizeof(tinstr)); > > tinstr = __mem_to_opcode_thumb16(tinstr); > > if (!fault) { > > if (cpu_architecture() >= CPU_ARCH_ARMv7 && > > IS_T32(tinstr)) { > > /* Thumb-2 32-bit */ > > u16 tinst2 = 0; > > - fault = probe_kernel_address(ptr + 1, tinst2); > > + fault = __copy_from_user(tinst2, > > + (__force const void __user *)(ptr+1), > > + sizeof(tinst2)); > > tinst2 = __mem_to_opcode_thumb16(tinst2); > > instr = __opcode_thumb32_compose(tinstr, tinst2); > > thumb2_32b = 1; > > @@ -803,10 +810,13 @@ static ssize_t alignment_proc_write(struct file *file, const char __user *buffer > > } > > } > > } else { > > - fault = probe_kernel_address((void *)instrptr, instr); > > + fault = __copy_from_user(instr, > > + (__force const void __user *)instrptr, > > + sizeof(instr)); > > instr = __mem_to_opcode_arm(instr); > > } > > > > + set_fs(fs); > > if (fault) { > > type = TYPE_FAULT; > > goto bad_or_fault; > > -- > > 1.8.3.1 > > > > > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up > According to speedtest.net: 11.9Mbps down 500kbps up > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel