On 3/12/2024 4:07 PM, Petr Tesarik wrote:
> On 2/23/2024 3:04 PM, Petr Tesarik wrote:
>> From: Petr Tesarik <petr.tesar...@huawei-partners.com>
>>
>> If a segmentation fault is caused by accessing an address in the vmalloc
>> area, check that the target page is present.
>>
>> Currently, if the kernel hits a guard page in the vmalloc area, UML blindly
>> assumes that the fault is caused by a stale mapping and will be fixed by
>> flush_tlb_kernel_vm(). Unsurprisingly, if the fault is caused by accessing
>> a guard page, no mapping is created, and when the faulting instruction is
>> restarted, it will cause exactly the same fault again, effectively creating
>> an infinite loop.
>
> Ping. Any comment on this fix?
I don't think I have seen a reply from you. If you did comment, then
your email has not reached me.
Please, can you confirm you have seen my patch?
Kind regards
Petr T
> Petr T
>
>>
>> Signed-off-by: Petr Tesarik <petr.tesar...@huawei-partners.com>
>> ---
>> arch/um/kernel/trap.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
>> index 6d8ae86ae978..d5b85f1bfe33 100644
>> --- a/arch/um/kernel/trap.c
>> +++ b/arch/um/kernel/trap.c
>> @@ -206,11 +206,15 @@ unsigned long segv(struct faultinfo fi, unsigned long
>> ip, int is_user,
>> int err;
>> int is_write = FAULT_WRITE(fi);
>> unsigned long address = FAULT_ADDRESS(fi);
>> + pte_t *pte;
>>
>> if (!is_user && regs)
>> current->thread.segv_regs = container_of(regs, struct pt_regs,
>> regs);
>>
>> if (!is_user && (address >= start_vm) && (address < end_vm)) {
>> + pte = virt_to_pte(&init_mm, address);
>> + if (!pte_present(*pte))
>> + page_fault_oops(regs, address, ip);
>> flush_tlb_kernel_vm();
>> goto out;
>> }
>
