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Re: [PATCH v2 3/3] xen/livepatch: Fix .altinstructions safety checks
- To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
- Date: Tue, 18 Apr 2023 16:25:51 +0000
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- Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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- Thread-topic: [PATCH v2 3/3] xen/livepatch: Fix .altinstructions safety checks
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: Monday, April 17, 2023 1:13 PM
> To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx>; Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> Subject: [PATCH v2 3/3] xen/livepatch: Fix .altinstructions safety checks
>
> The prior check has && vs || mixups, making it tautologically false and thus
> providing no safety at all. There are boundary errors too.
>
> First start with a comment describing how the .altinstructions and
> .altinstr_replacement sections interact, and perform suitable cross-checking.
>
> Second, rewrite the alt_instr loop entirely from scratch. Origin sites have
> non-zero size, and must be fully contained within the livepatches .text
> section(s). Any non-zero sized replacements must be fully contained within
> the .altinstr_replacement section.
>
> Fixes: f8a10174e8b1 ("xsplice: Add support for alternatives")
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
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