linux-kernel - Re: [PATCH][next] fs: Fix uninitialized scalar variable now

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Message-ID: <CAEO-vhGcPRQxzZBjDZZA4GZoWwcaOjgK85tUydvr9t7CtD-HGw@mail.gmail.com>
Date: Wed, 9 Oct 2024 15:46:58 -0600
From: "Everest K.C." <everestkc@...restkc.com.np>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz, 
	linux-fsdevel@...r.kernel.org, kernel-janitors@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] fs: Fix uninitialized scalar variable now

On Wed, Oct 9, 2024 at 2:38 PM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 10/9/24 14:05, Everest K.C. wrote:
> > Variable `now` is declared without initialization. The variable
> > could be accessed inside the if-else statements following the
> > variable declaration, before it has been initialized.
>
> It could be, but it isn't. I am not sure if this change is needed.
If you look at the full code then,  if  `ia_valid & ATTR_CTIME`
evaluates to False then now is never initialized.

> > This patch initializes the variable to
> > `inode_set_ctime_current(inode)` by default.
>
> Instead of "This patch initializes", change it to "Initialize ..."
> Do refer to submitting patches document for information on how
> to write change logs.
Will do that and send V2.
> >
> > This issue was reported by Coverity Scan.
>
> Include the the error/report from Coverity.
Will do that and send V2.
> >
> > Signed-off-by: Everest K.C. <everestkc@...restkc.com.np>
> > ---
> >   fs/attr.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/fs/attr.c b/fs/attr.c
> > index c614b954bda5..77523af2e62d 100644
> > --- a/fs/attr.c
> > +++ b/fs/attr.c
> > @@ -284,7 +284,7 @@ EXPORT_SYMBOL(inode_newsize_ok);
> >   static void setattr_copy_mgtime(struct inode *inode, const struct iattr *attr)
> >   {
> >       unsigned int ia_valid = attr->ia_valid;
> > -     struct timespec64 now;
> > +     struct timespec64 now = inode_set_ctime_current(inode);
> >
> >       if (ia_valid & ATTR_CTIME) {
> >               /*
> > @@ -293,8 +293,6 @@ static void setattr_copy_mgtime(struct inode *inode, const struct iattr *attr)
> >                */
> >               if (ia_valid & ATTR_DELEG)
> >                       now = inode_set_ctime_deleg(inode, attr->ia_ctime);
> > -             else
> > -                     now = inode_set_ctime_current(inode);
>
> The code is clear and easy to read the way it is since it handles both cases
> and does appropriate initialization.
Yes, I agree, but if we initialize now to the current time during its
declaration then the else
condition won't be necessary.
>
> >       } else {
> >               /* If ATTR_CTIME isn't set, then ATTR_MTIME shouldn't be either. */
> >               WARN_ON_ONCE(ia_valid & ATTR_MTIME);
>
> I will leave it up to the maintainers to decide whether to take
> this change or not.
>
> thanks,
> -- Shuah