From: Maxim Uvarov <muvarov@ru.mvista.com>
To: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Subject: Re: [MIPS] TLB handler fix for vmalloc'ed addresses
Date: Thu, 10 Sep 2009 18:37:47 +0400 [thread overview]
Message-ID: <4AA90F3B.6000204@ru.mvista.com> (raw)
In-Reply-To: <20090910141518.GA10547@linux-mips.org>
Ralf Baechle wrote:
> On Tue, Sep 08, 2009 at 05:06:32PM +0400, Maxim Uvarov wrote:
>
>> Patch is attached.
>
> Please send patches inline.
>
>> TLB exception handler incorrecly handles situation
>> with wrong vmalloc'ed addresses. This patch adds
>> verifications for vmalloc'ed addresses (similar to
>> x86_64 implementation). So the code now traps inside
>> do_page_fault() on access to the wrong area.
>>
>> Signed-off-by: Maxim Uvarov <muvarov@ru.mvista.com>
>>
>> Test case:
>>
>> #include <linux/module.h>
>> #include <linux/init.h>
>> #include <linux/kernel.h>
>> #include <linux/kthread.h>
>> #include <linux/delay.h>
>>
>> static struct task_struct *ts;
>> static int example_thread(void *dummy)
>> {
>> void *ptr;
>> ptr = vmalloc(16*1024*1024);
>> for(;;)
>> {
>> msleep(100);
>> }
>> }
>
> So your test case allocates vmalloc memory but never touches it.
Yes, it is so. Bug occurs on rmmod this module. (Module does not free memory
allocated with vmalloc().
>
>> static void run_vmalloc(void *unused)
>> {
>> ts=kthread_run(example_thread,NULL,"vtest");
>> }
>> int init_module (void)
>> {
>> run_vmalloc(NULL);
>> return 0;
>> }
>>
>> void cleanup_module (void)
>> { /*Nothing*/}
>>
>>
>> Originally kernel trapped on BUG() inside exit_mmap() and it was impossible
>> to see what has happened. After this patch applied, nice back trace will be
>> generated:
>>
>> CPU 0 Unable to handle kernel paging request at virtual address c00000000036a148
>> Oops[#1]:
>> Cpu 0
>> $ 0 : 0000000000000000 ffffffff81940000 0000000000000000 00000000ffff05a7
>> $ 4 : 0000000000000000 ffffffffffffffff ffffffff81a0b7d0 ffffffff811983e4
>> $ 8 : ffffffff817407b0 0000000000000000 0000000000000000 0000000000000000
>> $12 : a80000003374bfe0 0000000000008c00 ffffffff811e9df8 0000000000000000
>> $16 : ffffffff81164a68 a8000000352a3c50 c00000000036a0e8 0000000000000000
>> $20 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> $24 : 0000000000000002 a8000000337bb1a0
>> $28 : a800000033748000 a80000003374bf70 a80000003374bf70 c00000000036a148
>> Hi : 0000000000000000
>> Lo : 000000000000a311
>> epc : c00000000036a148 0xc00000000036a148 Tainted: P
>> ra : c00000000036a148 0xc00000000036a148 <-- dead in kernel module vtest
>> Status: 10008ce3 KX SX UX KERNEL EXL IE
>> Cause : 00000008
>> BadVA : c00000000036a148
>> PrId : 000d0408
>> Modules linked in:
>> Process vtest (pid: 723, threadinfo=a800000033748000, task=a800000034530340)
>> Stack : 0000000000000000 a80000003374bf90 ffffffff81176530 ffffffff81176488
>> ffffffffffffffff ffffffffffffffff 0000000000000000 0000000000000000
>> 0000000000000000 a80000003374bfd0 ffffffff81125024 0000000000000000
>> 0000000000000000 0000000000000000 5a5a5a5a5a5a5a5a 5a5a5a5a5a5a5a5a
>> 5a5a5a5a5a5a5a5a 5a5a5a5a5a5a5aa5
>> Call Trace:
>> [<ffffffff81176530>] kthread+0x198/0x1f0
>> [<ffffffff81176488>] kthread+0xf0/0x1f0
>> [<ffffffff81125024>] kernel_thread_helper+0x14/0x20
>>
>>
>> Code: (Bad address in epc)
>
> This is a 64-bit kernel crash ...
>
>> Index: linux-2.6.21/arch/mips/mm/fault.c
>> ===================================================================
>> --- linux-2.6.21.orig/arch/mips/mm/fault.c
>> +++ linux-2.6.21/arch/mips/mm/fault.c
>> @@ -282,22 +282,32 @@ vmalloc_fault:
>> pte_t *pte_k;
>>
>> pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
>> - pgd_k = init_mm.pgd + offset;
>> + pgd_k = pgd_offset_k(address);
>>
>> if (!pgd_present(*pgd_k))
>> goto no_context;
>> - set_pgd(pgd, *pgd_k);
>> + if (unlikely(!pgd_present(*pgd)))
>> + set_pgd(pgd, *pgd_k);
>> + else if (pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k))
>> + goto no_context;
>>
>> pud = pud_offset(pgd, address);
>> pud_k = pud_offset(pgd_k, address);
>> if (!pud_present(*pud_k))
>> goto no_context;
>> + if (pud_none(*pud) ||
>> + pud_page_vaddr(*pud) != pud_page_vaddr(*pud_k))
>> + goto no_context;
>>
>> pmd = pmd_offset(pud, address);
>> pmd_k = pmd_offset(pud_k, address);
>> if (!pmd_present(*pmd_k))
>> goto no_context;
>> - set_pmd(pmd, *pmd_k);
>> + if (!pmd_present(*pmd))
>> + set_pmd(pmd, *pmd_k);
>> + else
>> + if (pmd_page(*pmd) != pmd_page(*pmd_k))
>> + goto no_context;
>>
>> pte_k = pte_offset_kernel(pmd_k, address);
>> if (!pte_present(*pte_k))
>
> ... but on 64-bit kernels vmalloc_fault: should not be reached ever.
>
Ah. OK.
> Ralf
next prev parent reply other threads:[~2009-09-10 14:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-08 13:06 [MIPS] TLB handler fix for vmalloc'ed addresses Maxim Uvarov
2009-09-10 14:15 ` Ralf Baechle
2009-09-10 14:37 ` Maxim Uvarov [this message]
2009-09-10 15:37 ` Ralf Baechle
2009-09-10 15:48 ` Maxim Uvarov
2009-09-10 16:00 ` Maxim Uvarov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4AA90F3B.6000204@ru.mvista.com \
--to=muvarov@ru.mvista.com \
--cc=linux-mips@linux-mips.org \
--cc=ralf@linux-mips.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).