arm64: use RET instruction for exiting the trampoline

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Commit be04a6d112 upstream.

Speculation attacks against the entry trampoline can potentially resteer
the speculative instruction stream through the indirect branch and into
arbitrary gadgets within the kernel.

This patch defends against these attacks by forcing a misprediction
through the return stack: a dummy BL instruction loads an entry into
the stack, so that the predicted program flow of the subsequent RET
instruction is to a branch-to-self instruction which is finally resolved
as a branch to the kernel vectors with speculation suppressed.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Will Deacon 2017-11-14 16:15:59 +00:00 • committed by Greg Kroah-Hartman

parent 3882b5f63f

commit 68a65ce703

1 changed files with 9 additions and 1 deletions

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arch/arm64/kernel/entry.S

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