linux-kernel - Re: [PATCH] modules: Fix display of wrong module .text address

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Date:   Tue, 17 Apr 2018 13:20:00 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Christian Borntraeger <borntraeger@...ibm.com>
Cc:     Thomas Richter <tmricht@...ux.ibm.com>, jeyu@...nel.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        schwidefsky@...ibm.com, brueckner@...ux.vnet.ibm.com,
        heiko.carstens@...ibm.com, peterz@...radead.org, me@...in.cc,
        keescook@...omium.org
Subject: Re: [PATCH] modules: Fix display of wrong module .text address

Em Tue, Apr 17, 2018 at 10:24:35AM +0200, Christian Borntraeger escreveu:
> 
> 
> On 04/17/2018 10:20 AM, Thomas Richter wrote:
> > In kernel v4.16.0 the module .text address is displayed
> > wrong when using /sys/module/*/sections/.text file.
> > Commit ef0010a30935 ("vsprintf: don't use 'restricted_pointer()' when
> > not restricting")
> > is the first bad commit.
> > 
> > Here is the issue, using module qeth_l2 on s390 which is the
> > ethernet device driver:
> > 
> > [root@...lp76 ~]# lsmod
> > Module                  Size  Used by
> > qeth_l2                94208  1
> > ...
> > 
> > [root@...lp76 ~]# cat /proc/modules | egrep '^qeth_l2'
> > qeth_l2 94208 1 - Live 0x000003ff80401000
> >                        ^ This is the correct address in memory
> > [root@...lp76 ~]# cat /sys/module/qeth_l2/sections/.text
> > 0x0000000018ea8363      <---- This is a wrong address
> > [root@...lp76 ~]#
> > 
> > This breaks the perf tool which uses this address on s390
> > to calculate start of .text section in memory.
> > 
> > Fix this by printing the correct (unhashed) address.
> > 
> > Thanks to Jessica Yu for helping on this.
> > 
> > Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
> > Cc: Jessica Yu <jeyu@...nel.org>
> 
> CC stable?

Adding the missing:

Fixes: ef0010a30935 ("vsprintf: don't use 'restricted_pointer()' when not restricting")

Should be enough?

- Arnaldo
 
> > ---
> >  kernel/module.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/module.c b/kernel/module.c
> > index a6e43a5806a1..77ab7211ddef 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -1472,7 +1472,7 @@ static ssize_t module_sect_show(struct module_attribute *mattr,
> >  {
> >  	struct module_sect_attr *sattr =
> >  		container_of(mattr, struct module_sect_attr, mattr);
> > -	return sprintf(buf, "0x%pK\n", (void *)sattr->address);
> > +	return sprintf(buf, "%#lx\n", kptr_restrict < 2 ? sattr->address : 0);
> >  }
> >  
> >  static void free_sect_attrs(struct module_sect_attrs *sect_attrs)
> >