linux-kernel - Re: [PATCH v2] module: fix [e_shstrndx].sh

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Date:   Wed, 4 May 2022 13:30:16 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-modules@...r.kernel.org,
        Frank van der Linden <fllinden@...zon.com>
Subject: Re: [PATCH v2] module: fix [e_shstrndx].sh_size=0 OOB access

On Wed, May 04, 2022 at 12:54:20PM +0300, Alexey Dobriyan wrote:
> It is trivial to craft a module to trigger OOB access in this line:
> 
> 	if (info->secstrings[strhdr->sh_size - 1] != '\0') {
> 
> BUG: unable to handle page fault for address: ffffc90000aa0fff
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 100000067 P4D 100000067 PUD 100066067 PMD 10436f067 PTE 0
> Oops: 0000 [#1] PREEMPT SMP PTI
> CPU: 7 PID: 1215 Comm: insmod Not tainted 5.18.0-rc5-00007-g9bf578647087-dirty #10
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
> RIP: 0010:load_module+0x19b/0x2391
> 
> Fixes: ec2a29593c83 ("module: harden ELF info handling")
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>

Thanks! I rebased your patch onto modules-next [0] and applied onto
modules-testing and pushed out there. If that doesn't break I'll then
push to modules-next as well.

  Luis