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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=QniVckAJWtqLmmFgAWqtQvDUqGmhiEDDkK5Atd0uI+w=; b=Np6pBwhtLuvucwEiF287eQrxkwZd1Op2VN8YBDCUeGoFP3WyJP3wAlLyk74qzQP/Rh wLX87T3xq6rMdyK4yI8HPwwQIII3K3BGRtb/QyhMG8sXjnwEioh3v0SACpaCZ9MdXsUT lEciJMvx+7hXuwBlxUb0RfrgfkRQYK59tusSNsR/VJs9P29kBalRhflvBa29uHuRBlGp F049OeLKXXLVY/lvJx0wo7ExCWRtXA+mAEky1DxTlJ58LTvWrSlCBB1V5hebFHqCCYIv REd0H0rs1YxnOrc4pxUArF586qhy0mfVgNEQtzxiipmdBC27MOyS2flzCyOKZbVMqOhH Atyg== X-Gm-Message-State: APjAAAXNyvkehBR7m5N6HkDGsP5p7smdg38rr0jDVkNUAowNy+zTxvTD 0Ibm8AGBHp2qQY66XSv0fBWF/lrFDTq/iaF7GTc= X-Google-Smtp-Source: APXvYqwciBBhLealMEWoo9KoEMacGgV/WZH2VTZ4SCan5a+9yYr+272BEeKH1BEVWPC4FCthWzaq/J27w407jXSF4NM= X-Received: by 2002:a63:bc02:: with SMTP id q2mr24517139pge.174.1582070930907; Tue, 18 Feb 2020 16:08:50 -0800 (PST) Date: Tue, 18 Feb 2020 16:08:12 -0800 In-Reply-To: <20200219000817.195049-1-samitolvanen@google.com> Message-Id: <20200219000817.195049-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200219000817.195049-1-samitolvanen@google.com> X-Mailer: git-send-email 2.25.0.265.gbab2e86ba0-goog Subject: [PATCH v8 07/12] arm64: efi: restore x18 if it was corrupted From: Sami Tolvanen To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland , james.morse@arm.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200218_160852_673370_3290F698 X-CRM114-Status: GOOD ( 11.33 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:54a listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Masahiro Yamada , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , clang-built-linux@googlegroups.com, Sami Tolvanen , Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org If we detect a corrupted x18, restore the register before jumping back to potentially SCS instrumented code. This is safe, because the wrapper is called with preemption disabled and a separate shadow stack is used for interrupt handling. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Acked-by: Will Deacon --- arch/arm64/kernel/efi-rt-wrapper.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S index 3fc71106cb2b..6ca6c0dc11a1 100644 --- a/arch/arm64/kernel/efi-rt-wrapper.S +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -34,5 +34,14 @@ ENTRY(__efi_rt_asm_wrapper) ldp x29, x30, [sp], #32 b.ne 0f ret -0: b efi_handle_corrupted_x18 // tail call +0: + /* + * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a + * shadow stack pointer, which we need to restore before returning to + * potentially instrumented code. This is safe because the wrapper is + * called with preemption disabled and a separate shadow stack is used + * for interrupts. + */ + mov x18, x2 + b efi_handle_corrupted_x18 // tail call ENDPROC(__efi_rt_asm_wrapper)