linux-kernel - Re: kmemleaks on ac3b43283923 ("module: replace module_layout with module

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Message-ID: <ZCs6jpo1nYe1Wm08@bombadil.infradead.org>
Date:   Mon, 3 Apr 2023 13:43:58 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Song Liu <song@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     jim.cromie@...il.com, linux-modules@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Jason Baron <jbaron@...mai.com>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: kmemleaks on ac3b43283923 ("module: replace module_layout with
 module_memory")

On Fri, Mar 31, 2023 at 05:27:04PM -0700, Song Liu wrote:
> On Fri, Mar 31, 2023 at 12:00 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
> >
> > On Thu, Mar 30, 2023 at 04:45:43PM -0600, jim.cromie@...il.com wrote:
> > > hi Luis, etal
> > >
> > > kmemleak is reporting 19 leaks during boot
> > >
> > > because the hexdumps appeared to have module-names,
> > > and Ive been hacking nearby, and see the same names
> > > every time I boot my test-vm, I needed a clearer picture
> > > Jason corroborated and bisected.
> > >
> > > the 19 leaks split into 2 groups,
> > > 9 with names of builtin modules in the hexdump,
> > > all with the same backtrace
> > > 9 without module-names (with a shared backtrace)
> > > +1 wo name-ish and a separate backtrace
> >
> > Song, please take a look.
> 
> I will look into this next week.

I'm thinking this may be it, at least this gets us to what we used to do
as per original Catalinas' 4f2294b6dc88d ("kmemleak: Add modules
support") and right before Song's patch.

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 6b6da80f363f..3b9c71fa6096 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2240,7 +2240,10 @@ static int move_module(struct module *mod, struct load_info *info)
 		 * which is inside the block. Just mark it as not being a
 		 * leak.
 		 */
-		kmemleak_ignore(ptr);
+		if (type == MOD_INIT_TEXT)
+			kmemleak_ignore(ptr);
+		else
+			kmemleak_not_leak(ptr);
 		if (!ptr) {
 			t = type;
 			goto out_enomem;

We used to use the grey area for the TEXT but the original commit
doesn't explain too well why we grey out init but not the others. Ie
why kmemleak_ignore() on init and kmemleak_not_leak() on the others.

Catalinas, any thoughts / suggestions? Should we just stick to
kmemleak_not_leak() for both now?

  Luis