linux-kernel - Re: [PATCH] arm: uprobes: Don't hook on thumb instructions

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Message-ID: <875z17qw0z.wl-maz@kernel.org>
Date:   Wed, 31 Mar 2021 14:42:52 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Fredrik Strupe <fredrik@...upe.net>
Cc:     Russell King <linux@...linux.org.uk>, Rabin Vincent <rabin@....in>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: uprobes: Don't hook on thumb instructions

Hi Fredrik,

On  Mon, 18 May 2020, Fredrik Strupe wrote:
> Since uprobes is not supported for thumb, check that the thumb bit is
> not set when matching the uprobes instruction hooks.
>
> The Arm UDF instructions used for uprobes triggering
> (UPROBE_SWBP_ARM_INSN and UPROBE_SS_ARM_INSN) coincidentally share the
> same encoding as a pair of unallocated 32-bit thumb instructions (not
> UDF) when the condition code is 0b1111 (0xf). This in effect makes it
> possible to trigger the uprobes functionality from thumb, and at that
> using two unallocated instructions which are not permanently
> undefined.
>
> Signed-off-by: Fredrik Strupe <fredrik@...upe.net
> Fixes: c7edc9e326d5 ("ARM: add uprobes support")

It looks like we dropped the ball on this patch. Could you please add
it to Russell's patch system, together with a Cc: stable?

Otherwise, just say the word and I'll do it for you.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.