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| author | Will Deacon <will.deacon@arm.com> | 2017-11-14 19:15:59 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-01-08 21:43:31 +0300 |
| commit | be04a6d1126b02c6a28741155b899d648739fc5b (patch) | |
| tree | d5ef283426b675e5e8d776e70f6e4655f3437e2c | |
| parent | 3b3b681097fae73b7f5dcdd42db6cfdf32943d4c (diff) | |
| download | linux-be04a6d1126b02c6a28741155b899d648739fc5b.tar.xz | |
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: Catalin Marinas <catalin.marinas@arm.com>
| -rw-r--r-- | arch/arm64/kernel/entry.S | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 031392ee5f47..6ceed4877daf 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -1029,6 +1029,14 @@ alternative_else_nop_endif .if \regsize == 64 msr tpidrro_el0, x30 // Restored in kernel_ventry .endif + /* + * Defend against branch aliasing attacks by pushing a dummy + * entry onto the return stack and using a RET instruction to + * enter the full-fat kernel vectors. + */ + bl 2f + b . +2: tramp_map_kernel x30 #ifdef CONFIG_RANDOMIZE_BASE adr x30, tramp_vectors + PAGE_SIZE @@ -1041,7 +1049,7 @@ 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 |