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/
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next prev parent reply other threads:[~2019-08-30 13:35 UTC|newest]
Thread overview: 16+ 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 13:35 ` Russell King - ARM Linux admin [this message]
2019-08-30 13:48 ` Russell King - ARM Linux admin
2019-08-30 19:45 ` Eric W. Biederman
2019-08-30 20:30 ` Russell King - ARM Linux admin
2019-08-30 21:02 ` Eric W. Biederman
2019-08-30 22:29 ` Russell King - ARM Linux admin
2019-09-02 17:36 ` Eric W. Biederman
2019-09-04 2:17 ` Jing Xiangfeng
2019-09-06 15:17 ` Russell King - ARM Linux admin
2019-09-15 18:34 ` Russell King - ARM Linux admin
2019-09-16 14:31 ` Eric W. Biederman
2019-08-31 1:49 ` Jing Xiangfeng
2019-08-31 7:55 ` Russell King - ARM Linux admin
2019-08-31 9:16 ` Jing Xiangfeng
2019-08-31 12:48 ` kbuild test robot
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