• Will Deacon's avatar
    arm64: compat: Ensure upper 32 bits of x0 are zero on syscall return · 15956689
    Will Deacon authored
    Although we zero the upper bits of x0 on entry to the kernel from an
    AArch32 task, we do not clear them on the exception return path and can
    therefore expose 64-bit sign extended syscall return values to userspace
    via interfaces such as the 'perf_regs' ABI, which deal exclusively with
    64-bit registers.
    
    Explicitly clear the upper 32 bits of x0 on return from a compat system
    call.
    
    Cc: <stable@vger.kernel.org>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Keno Fischer <keno@juliacomputing.com>
    Cc: Luis Machado <luis.machado@linaro.org>
    Signed-off-by: default avatarWill Deacon <will@kernel.org>
    15956689
syscall.c 4.79 KB