linux-kernel - Re: [PATCH] arch/x86/um: Disable UBSAN sanitization

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Message-ID: <505192e0d4a8d336ff0e934590c761de3a72e3a9.camel@huaweicloud.com>
Date: Mon, 13 May 2024 15:16:55 +0200
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Johannes Berg <johannes@...solutions.net>, richard@....at, 
	anton.ivanov@...bridgegreys.com, tglx@...utronix.de, mingo@...hat.com, 
	bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com
Cc: x86@...nel.org, linux-um@...ts.infradead.org,
 linux-kernel@...r.kernel.org,  zohar@...ux.ibm.com,
 linux-integrity@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH] arch/x86/um: Disable UBSAN sanitization

On Mon, 2024-05-13 at 15:08 +0200, Johannes Berg wrote:
> On Mon, 2024-05-13 at 14:58 +0200, Roberto Sassu wrote:
> > On Mon, 2024-05-13 at 14:52 +0200, Johannes Berg wrote:
> > > On Mon, 2024-05-13 at 14:42 +0200, Roberto Sassu wrote:
> > > > On Mon, 2024-05-13 at 14:29 +0200, Johannes Berg wrote:
> > > > > On Mon, 2024-05-13 at 14:27 +0200, Roberto Sassu wrote:
> > > > > > From: Roberto Sassu <roberto.sassu@...wei.com>
> > > > > > 
> > > > > > Disable UBSAN sanitization on UML, since UML does not support it.
> > > > > > 
> > > > > 
> > > > > Luckily, that isn't actually true, nor does it actually do this at all.
> > > > > Please fix the commit message.
> > > > 
> > > > Thanks, I was actually wondering. I based that statement based on
> > > > ARCH_HAS_UBSAN=n.
> > > > 
> > > > Any other solution would be ok.
> > > 
> > > Not sure I get it. What you're doing in the patch is perfectly fine and
> > > almost certainly required, but you're definitely not disabling UBSAN on
> > > ARCH=um as you described in the commit message?
> > 
> > Ok, I guess the right word is instrumentation (got it from commit
> > d4be85d068b44). And the reason is that the vDSO is executing in user
> > space. Will fix it.
> 
> No, UBSAN is fine, but you're only disabling it for the vDSO :) The
> commit message doesn't even mention the vDSO though.

You are right, the commit message was misleading without vDSO.

Thanks

Roberto