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

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Message-ID: <CAEO-vhECze1oN89+Pj0A8bMDZbCzHzLkRb+2F2aw+tcxAevuAg@mail.gmail.com>
Date: Wed, 9 Oct 2024 16:55:39 -0600
From: "Everest K.C." <everestkc@...restkc.com.np>
To: Jeff Layton <jlayton@...nel.org>
Cc: Dan Carpenter <dan.carpenter@...aro.org>, viro@...iv.linux.org.uk, brauner@...nel.org, 
	jack@...e.cz, skhan@...uxfoundation.org, 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 4:40 PM Jeff Layton <jlayton@...nel.org> wrote:
>
> On Wed, 2024-10-09 at 23:45 +0300, Dan Carpenter wrote:
> > On Wed, Oct 09, 2024 at 02:05:25PM -0600, 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.
> > >
> > > This patch initializes the variable to
> > > `inode_set_ctime_current(inode)` by default.
> > >
> > > This issue was reported by Coverity Scan.
> > >
> > > Signed-off-by: Everest K.C. <everestkc@...restkc.com.np>
> >
> > Fixes: d8d11298e8a1 ("fs: handle delegated timestamps in setattr_copy_mgtime")
> >
> > Maybe the WARN_ON_ONCE() should be updated to check ATTR_ATIME as well?
> >
> > regards,
> > dan carpenter
> >
> > > ---
> > >  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);
> > >     } else {
> > >             /* If ATTR_CTIME isn't set, then ATTR_MTIME shouldn't be either. */
> > >             WARN_ON_ONCE(ia_valid & ATTR_MTIME);
> > > --
> > > 2.43.0
> > >
>
> This doesn't look correct. inode_set_ctime_current will update the time
> to the current time and then inode_set_ctime_deleg() won't work
> properly if the time being set is earlier than that.
Yes. I get it now.
> I proposed a different fix earlier today which should be correct:
>
> https://lore.kernel.org/linux-fsdevel/20241009-mgtime-v1-1-383b9e0481b5@kernel.org/
> Thanks,
> --
> Jeff Layton <jlayton@...nel.org>
Thanks,
Everest K.C.