From: Russell King - ARM Linux admin <linux@armlinux.org.uk> To: Jing Xiangfeng <jingxiangfeng@huawei.com> Cc: ebiederm@xmission.com, kstewart@linuxfoundation.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, bhelgaas@google.com, tglx@linutronix.de, sakari.ailus@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] arm: fix page faults in do_alignment Date: Fri, 30 Aug 2019 14:35:22 +0100 [thread overview] Message-ID: <20190830133522.GZ13294@shell.armlinux.org.uk> (raw) In-Reply-To: <1567171877-101949-1-git-send-email-jingxiangfeng@huawei.com> 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 <jingxiangfeng@huawei.com> 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
WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk> To: Jing Xiangfeng <jingxiangfeng@huawei.com> 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 Subject: Re: [PATCH] arm: fix page faults in do_alignment Date: Fri, 30 Aug 2019 14:35:22 +0100 [thread overview] Message-ID: <20190830133522.GZ13294@shell.armlinux.org.uk> (raw) In-Reply-To: <1567171877-101949-1-git-send-email-jingxiangfeng@huawei.com> 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 <jingxiangfeng@huawei.com> 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
next prev parent reply other threads:[~2019-08-30 13:35 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-08-30 13:31 [PATCH] arm: fix page faults in do_alignment Jing Xiangfeng 2019-08-30 13:31 ` Jing Xiangfeng 2019-08-30 13:35 ` Russell King - ARM Linux admin [this message] 2019-08-30 13:35 ` Russell King - ARM Linux admin 2019-08-30 13:48 ` Russell King - ARM Linux admin 2019-08-30 13:48 ` Russell King - ARM Linux admin 2019-08-30 19:45 ` Eric W. Biederman 2019-08-30 19:45 ` Eric W. Biederman 2019-08-30 19:45 ` Eric W. Biederman 2019-08-30 20:30 ` Russell King - ARM Linux admin 2019-08-30 20:30 ` Russell King - ARM Linux admin 2019-08-30 21:02 ` Eric W. Biederman 2019-08-30 21:02 ` Eric W. Biederman 2019-08-30 21:02 ` Eric W. Biederman 2019-08-30 22:29 ` Russell King - ARM Linux admin 2019-08-30 22:29 ` Russell King - ARM Linux admin 2019-09-02 17:36 ` Eric W. Biederman 2019-09-02 17:36 ` Eric W. Biederman 2019-09-02 17:36 ` Eric W. Biederman 2019-09-04 2:17 ` Jing Xiangfeng 2019-09-04 2:17 ` Jing Xiangfeng 2019-09-06 15:17 ` Russell King - ARM Linux admin 2019-09-06 15:17 ` Russell King - ARM Linux admin 2019-09-15 18:34 ` Russell King - ARM Linux admin 2019-09-15 18:34 ` Russell King - ARM Linux admin 2019-09-16 14:31 ` Eric W. Biederman 2019-09-16 14:31 ` Eric W. Biederman 2019-09-16 14:31 ` Eric W. Biederman 2019-08-31 1:49 ` Jing Xiangfeng 2019-08-31 1:49 ` Jing Xiangfeng 2019-08-31 7:55 ` Russell King - ARM Linux admin 2019-08-31 7:55 ` Russell King - ARM Linux admin 2019-08-31 9:16 ` Jing Xiangfeng 2019-08-31 9:16 ` Jing Xiangfeng 2019-08-31 12:48 ` kbuild test robot
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