linux-kernel - Re: [RFC PATCH tip] rseq: Fix: Increase AT_VECTOR_SIZE

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Message-ID: <Y7XSWdLZqwEXWXml@dev-arch.thelio-3990X>
Date:   Wed, 4 Jan 2023 12:24:09 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api@...r.kernel.org, Christian Brauner <brauner@...nel.org>,
        Florian Weimer <fw@...eb.enyo.de>, David.Laight@...lab.com,
        carlos@...hat.com, Peter Oskolkov <posk@...k.io>,
        Alexander Mikhalitsyn <alexander@...alicyn.com>,
        Chris Kennelly <ckennelly@...gle.com>
Subject: Re: [RFC PATCH tip] rseq: Fix: Increase AT_VECTOR_SIZE_BASE to match
 rseq auxvec entries

On Wed, Jan 04, 2023 at 02:20:54PM -0500, Mathieu Desnoyers wrote:
> Two new auxiliary vector entries are introduced for rseq without
> matching increment of the AT_VECTOR_SIZE_BASE, which causes failures
> with CONFIG_HARDENED_USERCOPY=y.
> 
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Link: https://lore.kernel.org/r/Y7XJKZhuU9VJZQ11@dev-arch.thelio-3990X
> Fixes: 317c8194e6ae ("rseq: Introduce feature size and alignment ELF auxiliary vector entries")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

This resolves the boot failure with the configuration I tested:

Tested-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  include/linux/auxvec.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/auxvec.h b/include/linux/auxvec.h
> index f68d0ec2d740..407f7005e6d6 100644
> --- a/include/linux/auxvec.h
> +++ b/include/linux/auxvec.h
> @@ -4,6 +4,6 @@
>  
>  #include <uapi/linux/auxvec.h>
>  
> -#define AT_VECTOR_SIZE_BASE 20 /* NEW_AUX_ENT entries in auxiliary table */
> +#define AT_VECTOR_SIZE_BASE 22 /* NEW_AUX_ENT entries in auxiliary table */
>    /* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */
>  #endif /* _LINUX_AUXVEC_H */
> -- 
> 2.25.1
>