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

Mark Rutland [off-list ref] 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@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Punit Agrawal <redacted>
Cc: Will Deacon <redacted>

From the description, the problem looks quite serious. I'm surprised

this hasn't exploded before.

FWIW,

        Acked-by: Punit Agrawal [off-list ref]

Thanks!


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