Re: [tip:x86/pti] x86/asm: Pad assembly functions with INT3 instructions

From: Mike Galbraith
Date: Sun Jun 17 2018 - 09:39:59 EST


On Sun, 2018-06-17 at 14:00 +0200, Borislav Petkov wrote:
> On Sun, Jun 17, 2018 at 01:40:13PM +0200, Mike Galbraith wrote:
> > On Mon, 2018-05-14 at 05:53 -0700, tip-bot for Alexey Dobriyan wrote:
> > > Commit-ID: 51bad67ffbce0aaa44579f84ef5d05597054ec6a
> > > Gitweb: https://git.kernel.org/tip/51bad67ffbce0aaa44579f84ef5d05597054ec6a
> > > Author: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> > > AuthorDate: Tue, 8 May 2018 00:37:55 +0300
> > > Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> > > CommitDate: Mon, 14 May 2018 11:43:03 +0200
> > >
> > > x86/asm: Pad assembly functions with INT3 instructions
> > >
> > > Use INT3 instead of NOP. All that padding between functions is
> > > an illegal area, no legitimate code should jump into it.
> >
> > Is dinky patchlet suggesting cryptomgr is being naughty?
> >
> > (revert silences spew, but..)
> >
> > ...
> > [ 21.041608] int3: 0000 [#1] SMP PTI
> > [ 21.041754] CPU: 3 PID: 935 Comm: cryptomgr_test Tainted: G E 4.17.0.g075a1d3-tip-default #146
> > [ 21.041888] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
> > [ 21.042035] RIP: 0010:crypto_aegis128_aesni_enc_tail+0x74/0x80 [aegis128_aesni]
> > [ 21.042171] Code: 38 dc ca 66 0f 38 dc d3 66 0f 38 dc de 66 0f ef e5 f3 0f 7f 27 f3 0f 7f 47 10 f3 0f 7f 4f 20 f3 0f 7f 57 30 f3 0f 7f 5f 40 cc <cc> cc cc cc cc cc cc cc cc cc cc cc 48 83 fe 10 0f 82 c3 03 00 00
>
> Looks like it misses a RET:

Bingo.

[ 28.751069] RIP: 0010:crypto_aegis128l_aesni_enc_tail+0xcd/0xd0 [aegis128l_aesni]

Next next next..

> ---
> From 6ac281ee69f4cb5b581d5f49662fb56b6326155a Mon Sep 17 00:00:00 2001
> From: Borislav Petkov <bp@xxxxxxx>
> Date: Sun, 17 Jun 2018 13:57:42 +0200
> Subject: [PATCH] x86/crypto: Add a missing RET
>
> crypto_aegis128_aesni_enc_tail() needs to return too.
>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> ---
> arch/x86/crypto/aegis128-aesni-asm.S | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/crypto/aegis128-aesni-asm.S b/arch/x86/crypto/aegis128-aesni-asm.S
> index 9254e0b6cc06..717bf0776421 100644
> --- a/arch/x86/crypto/aegis128-aesni-asm.S
> +++ b/arch/x86/crypto/aegis128-aesni-asm.S
> @@ -535,6 +535,7 @@ ENTRY(crypto_aegis128_aesni_enc_tail)
> movdqu STATE3, 0x40(STATEP)
>
> FRAME_END
> + ret
> ENDPROC(crypto_aegis128_aesni_enc_tail)
>
> .macro decrypt_block a s0 s1 s2 s3 s4 i
> --
> 2.17.0.582.gccdcbd54c
>