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Re: [RFC PATCH v1] arch/x86: Livepatch: fix overflow check when computing ELF relocations
- To: Bjoern Doebel <doebel@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 8 Mar 2022 16:45:34 +0100
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- Cc: Michael Kurth <mku@xxxxxxxxx>, Martin Pohlack <mpohlack@xxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 08 Mar 2022 15:45:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.03.2022 16:36, Bjoern Doebel wrote:
> --- a/xen/arch/x86/livepatch.c
> +++ b/xen/arch/x86/livepatch.c
> @@ -339,7 +339,7 @@ int arch_livepatch_perform_rela(struct livepatch_elf *elf,
>
> val -= (uint64_t)dest;
> *(int32_t *)dest = val;
Afaict after this assignment ...
> - if ( (int64_t)val != *(int32_t *)dest )
> + if ( (int32_t)val != *(int32_t *)dest )
... this condition can never be false. The cast really wants to be
to int64_t, and the overflow you saw being reported is quite likely
for a different reason. But from the sole message you did quote
it's not really possible to figure what else is wrong.
Jan
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