linux-kernel - Re: [PATCH] fs/seq_file: Fix warning of passing zero to 'PTR

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Date:   Fri, 8 Dec 2017 08:54:34 +0100
From:   "Gomonovych, Vasyl" <gomonovych@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>, willy@...radead.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/seq_file: Fix warning of passing zero to 'PTR_ERR'

Hi,

Guys sorry for this idiotic piece of code.
Yesterday after doc seq_file.txt read I did not catch real way of work there.
And made this shit.
Sorry.

Regards Vasyl

On Fri, Dec 8, 2017 at 12:26 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Thu, Dec 07, 2017 at 11:23:26PM +0000, Al Viro wrote:
>> On Fri, Dec 08, 2017 at 12:03:07AM +0100, Vasyl Gomonovych wrote:
>> > p could be NULL and passing into PTR_ERR
>> >
>> > Signed-off-by: Vasyl Gomonovych <gomonovych@...il.com>
>> > ---
>> >  fs/seq_file.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/fs/seq_file.c b/fs/seq_file.c
>> > index 4be761c..8b700b9 100644
>> > --- a/fs/seq_file.c
>> > +++ b/fs/seq_file.c
>> > @@ -262,8 +262,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
>> >             size_t offs = m->count;
>> >             loff_t next = pos;
>> >             p = m->op->next(m, p, &next);
>> > -           if (!p || IS_ERR(p)) {
>> > -                   err = PTR_ERR(p);
>> > +           if (IS_ERR(p)) {
>> > +                   err = (!p ? -EFAULT : PTR_ERR(p));
>>
>> What does it fix, if I might ask?  And while we are at it, would
>> you mind explaining the reasoning behind that change?  Or, say,
>> testing done to it...
>
> While we are at it, where has that -EFAULT come from?  And how
> would it be ever reached, seeing that IS_ERR(NULL) is false?



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