linux-kernel - Re: [PATCH v3] proc/kcore: fix invalid memory access in multi-page read optimization

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Message-ID: <CACi5LpNVCXXPnWMAabUxFBKW7R9rH5vKVE0DZ3NENOM_nFAZrw@mail.gmail.com>
Date:   Thu, 6 Sep 2018 01:26:47 +0530
From:   Bhupesh Sharma <bhsharma@...hat.com>
To:     Omar Sandoval <osandov@...ndov.com>
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        James Morse <james.morse@....com>, kernel-team@...com
Subject: Re: [PATCH v3] proc/kcore: fix invalid memory access in multi-page
 read optimization

On Wed, Sep 5, 2018 at 4:11 AM, Omar Sandoval <osandov@...ndov.com> wrote:
> On Wed, Sep 05, 2018 at 12:38:22AM +0200, Dominique Martinet wrote:
>> The 'm' kcore_list item could point to kclist_head, and it is incorrect to
>> look at m->addr / m->size in this case.
>> There is no choice but to run through the list of entries for every address
>> if we did not find any entry in the previous iteration
>>
>> Reset 'm' to NULL in that case at Omar Sandoval's suggestion.
>>
>> Fixes: bf991c2231117 ("proc/kcore: optimize multiple page reads")
>
> Reviewed-by: Omar Sandoval <osandov@...com>
>
> Thanks again for catching this!
>
>> Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
>> ---
>>
>> Sorry, resent v2 because From didn't match sob tag
>>
>>  fs/proc/kcore.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
>> index ad72261ee3fe..578926032880 100644
>> --- a/fs/proc/kcore.c
>> +++ b/fs/proc/kcore.c
>> @@ -464,6 +464,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
>>                               ret = -EFAULT;
>>                               goto out;
>>                       }
>> +                     m = NULL;
>>               } else if (m->type == KCORE_VMALLOC) {
>>                       vread(buf, (char *)start, tsz);
>>                       /* we have to zero-fill user buffer even if no read */
>> --
>> 2.17.1

Looks sane to me, so:

Reviewed-by: Bhupesh Sharma <bhsharma@...hat.com>

Thanks.