diff options
| author | Will Deacon <will.deacon@arm.com> | 2017-11-14 16:15:59 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@google.com> | 2018-01-06 12:41:50 +0100 |
| commit | 753593688bfab89b6cbf085f62fec44012a6820d (patch) | |
| tree | f9472314cf74037c7a46a71e6ecf1fe33c2902da | |
| parent | 06fe41f85237c9d3c915447b9f9d51f1e85c4891 (diff) | |
arm64: use RET instruction for exiting the trampoline
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: Greg Kroah-Hartman <gregkh@google.com>
| -rw-r--r-- | arch/arm64/kernel/entry.S | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index fe22ca8ae750..c1ff0999045e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -948,6 +948,9 @@ __ni_sys_trace: .if \regsize == 64 msr tpidrro_el0, x30 // Restored in kernel_ventry .endif + bl 2f + b . +2: tramp_map_kernel x30 #ifdef CONFIG_RANDOMIZE_BASE adr x30, tramp_vectors + PAGE_SIZE @@ -960,7 +963,7 @@ alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003 msr vbar_el1, x30 add x30, x30, #(1b - tramp_vectors) isb - br x30 + ret .endm .macro tramp_exit, regsize = 64 |