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SubjectRe: Seq File: Return error if d_path fails
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Hi Andrew,

On Tue, Aug 13, 2013 at 3:19 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Thu, 8 Aug 2013 19:03:31 +0530 Arun KS <arunks.linux@gmail.com> wrote:
>
>> >From 2558382c8a030f7261e47977ac62412cd78e6d38 Mon Sep 17 00:00:00 2001
>> From: Arun KS <arun.ks@broadcom.com>
>> Date: Thu, 8 Aug 2013 18:23:04 +0530
>> Subject: Seq File: Return error if d_path fails
>>
>> Return error if d_path fails in seq_path funciton. If we do not return
>> from here,
>> seq_commit sets seq_file state as overflow. And this continues in a
>> loop utill we
>> increase the size of seq buf beyond KMALLOC_MAX_SIZE.
>>
>> ...
>>
>> --- a/fs/seq_file.c
>> +++ b/fs/seq_file.c
>> @@ -471,7 +471,8 @@ int seq_path(struct seq_file *m, const struct path
>> *path, const char *esc)
>> char *end = mangle_path(buf, p, esc);
>> if (end)
>> res = end - buf;
>> - }
>> + } else
>> + return PTR_ERR(p);
>> }
>> seq_commit(m, res);
>
> hm, does that really fix the bug? Isn't the core problem the word "or":
>
> /**
> * seq_commit - commit data to the buffer
> * @m: the seq_file handle
> * @num: the number of bytes to commit
> *
> * Commit @num bytes of data written to a buffer previously acquired
> * by seq_buf_get. To signal an error condition, or that the data
> ^^
> * didn't fit in the available space, pass a negative @num value.
> */
>
> seq_path()/seq_commit() is treating a d_path() failure as an overflow
> condition, but it isn't.
>
I ll send a new patch.

Thanks,
Arun


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