[PATCH 4/6] arm64: armv8_deprecated: ensure extension of addr

[Punit Agrawal]

Mark Rutland <mark.rutland at arm.com> writes:

> Our compat swp emulation holds the compat user address in an unsigned
> int, which it passes to __user_swpX_asm(). When a 32-bit value is passed
> in a register, the upper 32 bits of the register are unknown, and we
> must extend the value to 64 bits before we can use it as a base address.
>
> This patch casts the address to unsigned long to ensure it has been
> suitably extended, avoiding the potential issue, and silencing a related
> warning from clang.
>
> Fixes: bd35a4adc4131c53 ("arm64: Port SWP/SWPB emulation support from arm")
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Matthias Kaehlcke <mka at chromium.org>
> Cc: Punit Agrawal <punit.agrawal at arm.com>
> Cc: Will Deacon <will.deacon at arm.com>

>From the description, the problem looks quite serious. I'm surprised
this hasn't exploded before.

FWIW,

        Acked-by: Punit Agrawal <punit.agrawal at arm.com>

Thanks!


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