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ARM: mm: fix alignment handler faults under memory pressure 

When the system has high memory pressure, the page containing the
instruction may be paged out.  Using probe_kernel_address() means that
if the page is swapped out, the resulting page fault will not be
handled because page faults are disabled by this function.

Use get_user() to read the instruction instead.

Reported-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Fixes: b255188f90 ("ARM: fix scheduling while atomic warning in alignment handling code")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2019-08-31 17:01:58 +01:00
parent 4d856f72c1
commit 67e15fa5b4
1 changed files with 36 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
arch/arm/mm/alignment.c
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@ -767,6 +767,36 @@ do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
return NULL;
}
static int alignment_get_arm(struct pt_regs *regs, u32 *ip, unsigned long *inst)
{
u32 instr = 0;
int fault;
if (user_mode(regs))
fault = get_user(instr, ip);
else
fault = probe_kernel_address(ip, instr);
*inst = __mem_to_opcode_arm(instr);
return fault;
}
static int alignment_get_thumb(struct pt_regs *regs, u16 *ip, u16 *inst)
{
u16 instr = 0;
int fault;
if (user_mode(regs))
fault = get_user(instr, ip);
else
fault = probe_kernel_address(ip, instr);
*inst = __mem_to_opcode_thumb16(instr);
return fault;
}
static int
do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
@ -774,10 +804,10 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
unsigned long instr = 0, instrptr;
int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
unsigned int type;
unsigned int fault;
u16 tinstr = 0;
int isize = 4;
int thumb2_32b = 0;
int fault;
if (interrupts_enabled(regs))
local_irq_enable();
@ -786,15 +816,14 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
if (thumb_mode(regs)) {
u16 *ptr = (u16 *)(instrptr & ~1);
fault = probe_kernel_address(ptr, tinstr);
tinstr = __mem_to_opcode_thumb16(tinstr);
fault = alignment_get_thumb(regs, ptr, &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);
tinst2 = __mem_to_opcode_thumb16(tinst2);
u16 tinst2;
fault = alignment_get_thumb(regs, ptr + 1, &tinst2);
instr = __opcode_thumb32_compose(tinstr, tinst2);
thumb2_32b = 1;
} else {
@ -803,8 +832,7 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
}
}
} else {
fault = probe_kernel_address((void *)instrptr, instr);
instr = __mem_to_opcode_arm(instr);
fault = alignment_get_arm(regs, (void *)instrptr, &instr);
}
if (fault) {