linux-kernel - Re: [PATCH 1/4] sysctl: move u8 register test to lib/test

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Message-ID: <ncfru3u5wwbnsdtehdwecaihhxy4kdhn4ip5nyno7o7fgatwaw@rjp73b4nu7ci>
Date: Fri, 11 Apr 2025 14:37:40 +0200
From: Joel Granados <joel.granados@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Shuah Khan <shuah@...nel.org>, John Sperbeck <jsperbeck@...gle.com>, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 1/4] sysctl: move u8 register test to lib/test_sysctl.c

On Wed, Apr 09, 2025 at 10:26:56AM -0700, Kees Cook wrote:
> On Fri, Mar 21, 2025 at 01:47:24PM +0100, Joel Granados wrote:
> > If the test added in commit b5ffbd139688 ("sysctl: move the extra1/2
> > boundary check of u8 to sysctl_check_table_array") is run as a module, a
> > lingering reference to the module is left behind, and a 'sysctl -a'
> > leads to a panic.
> > 
> > To reproduce
> >     CONFIG_KUNIT=y
> >     CONFIG_SYSCTL_KUNIT_TEST=m
> > 
> > Then run these commands:
> >     modprobe sysctl-test
> >     rmmod sysctl-test
> >     sysctl -a
> > 
> > The panic varies but generally looks something like this:
> > 
> >     BUG: unable to handle page fault for address: ffffa4571c0c7db4
> >     #PF: supervisor read access in kernel mode
> >     #PF: error_code(0x0000) - not-present page
> >     PGD 100000067 P4D 100000067 PUD 100351067 PMD 114f5e067 PTE 0
> >     Oops: Oops: 0000 [#1] SMP NOPTI
> >     ... ... ...
> >     RIP: 0010:proc_sys_readdir+0x166/0x2c0
> >     ... ... ...
> >     Call Trace:
> >      <TASK>
> >      iterate_dir+0x6e/0x140
> >      __se_sys_getdents+0x6e/0x100
> >      do_syscall_64+0x70/0x150
> >      entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > 
> > Move the test to lib/test_sysctl.c where the registration reference is
> > handled on module exit
> > 
> > 'Fixes: b5ffbd139688 ("sysctl: move the extra1/2 boundary check of u8 to
> 
> Typoe: drop leading '
> 
> > sysctl_check_table_array")'
> 
> And avoid wrapping this line for the field.
> 
> > 
> > Signed-off-by: Joel Granados <joel.granados@...nel.org>
> 
> Otherwise looks good to me.

Thx for the feedback; 
Changed this and took in your trailers, but wont resend.

Best
-- 

Joel Granados

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