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From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [GIT PULL] ftrace: Check if pages were allocated before calling free_pages()
Date: Thu, 1 Apr 2021 16:53:04 -0400	[thread overview]
Message-ID: <20210401165304.187c7f7e@gandalf.local.home> (raw)
In-Reply-To: <CAHk-=wg_6JBGSiKtQp7CT99kFt2L5b1sbvs6YBTXJAWdPc8Hig@mail.gmail.com>

On Thu, 1 Apr 2021 13:18:59 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, Apr 1, 2021 at 1:07 PM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > On Wed, 31 Mar 2021 11:03:21 -0700
> > Linus Torvalds <torvalds@linux-foundation.org> wrote:
> >
> > > @@ -6231,7 +6231,8 @@ static int ftrace_process_locs(struct module *mod,
> > >               if (!addr)
> > >                       continue;
> > >
> > > -             if (pg->index == pg->size) {
> > > +             end_offset = (pg->index+1) * sizeof(pg->records[0]);
> > > +             if (end_offset < PAGE_SIZE << pg->order) {
> >
> > I believe that needs to be:
> >
> >         if (end_offset >= PAGE_SIZE << pg->order) {
> 

[..]

> which will be
> 
>         end_offset = (3+1) * 1024;
> 
> ie 4096. That just means that the struct fill fill things _up_to_ the
> end of the page.
> 
> So only when the end_offset is strictly larger than the page would it
> have overflowed the allocation.

Ah, I forgot about the "+1" you added to the pg->index, which would make it
equivalent to replacing:

	if (pg->index + 1 > pg->size) {


Will update and add your SOB.

Thanks,

-- Steve


  reply	other threads:[~2021-04-01 20:53 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-31 13:27 [GIT PULL] ftrace: Check if pages were allocated before calling free_pages() Steven Rostedt
2021-03-31 17:45 ` Linus Torvalds
2021-03-31 18:03   ` Linus Torvalds
2021-03-31 19:03     ` Steven Rostedt
2021-04-01 20:07     ` Steven Rostedt
2021-04-01 20:18       ` Linus Torvalds
2021-04-01 20:53         ` Steven Rostedt [this message]
2021-04-01 20:25       ` Steven Rostedt
2021-03-31 18:51   ` Steven Rostedt
2021-03-31 19:01     ` Linus Torvalds
2021-03-31 18:05 ` pr-tracker-bot

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