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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id t15-20020a1709027fcf00b001bb9d6b1baasm1004673plb.198.2023.08.04.00.10.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Aug 2023 00:10:56 -0700 (PDT) From: Kees Cook To: Russell King Cc: Kees Cook , Arnd Bergmann , Lecopzer Chen , Oleg Nesterov , linux-arm-kernel@lists.infradead.org, Linus Walleij , "Russell King (Oracle)" , linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-hardening@vger.kernel.org Subject: [PATCH] ARM: ptrace: Restore syscall skipping and restart while tracing Date: Fri, 4 Aug 2023 00:10:53 -0700 Message-Id: <20230804071045.never.134-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3616; i=keescook@chromium.org; h=from:subject:message-id; bh=YJOlkz5vR8N2JtifY2dbTGKNtQ5WuTgnR2Q8FS+sopI=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBkzKR9I86BSc6Kgktbv/7TDrdJhNiDSv95T3xHY eyI/ytlKbuJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZMykfQAKCRCJcvTf3G3A Jik5D/wJIILgmLRP6PaC7n466O199JDTx/nN4iSx3/PxF6xa5b2VxRNepGSXm+bdcy5M4OqFg3r TA1mKMteXSnWTrbT6GiBIpzbb7RZFqHQOobd5wekGbI0n067nE+ORmctWJhm+Ez+ND7kvimDYsA m0J22/G7zNs0ra32uU0923Itwf0Ecq3IpRk6/Nq0Thkqs6Ske3CEnT7knCi/TW2wVVRFaYYGBg4 JRpm78U3nRqxZZKGzRMHXrjS+C0zpxMYb/mAi70Gqst2Cv8SQ6zG+AF+0yXYHtn9nDL6cpYs/zg 2RJt+z6nn1dc1PjKFW2epvs50HQWpZ6bxr27B9saaxelsggIzQvZiSP3kRP20HiSKuy15PBpfCt lPiwqMq/vdC+jkApGPq34GOt5QykWpS6foa957+wSOq8zGbgJ+P6VR9dABq/CWSKdpYo8u8Rq1Q QivGh6o9OZTwFFf+tzPyFnrCP8vukNObnld8PCe9Fb2ZReOQa7Q0dce7AWkvt6u0DflPGvGr9NT wFVfmqWQUQRZ4u9BQS/OSWloz11A49wuJuNiBnO43ROHdO94wjO1qs4Z5Iz4X4KfaUUsSguYalJ H4OwKyvCk8gKBRbgGrvrMqp4nQvKxVditb2rk2EjVJEARIxXoYwJwZEmcJEeKbv2JPCRnqimCs/ PCY1+m3 4PNLqCLQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Since commit 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall"), the seccomp selftests "syscall_errno", "syscall_faked", and "syscall_restart" have been broken. This was related to two issues: - seccomp and PTRACE depend on using the special value of "-1" for skipping syscalls. This value wasn't working because it was getting masked by __NR_SYSCALL_MASK in both PTRACE_SET_SYSCALL and get_syscall_nr(). - the syscall entry label "local_restart" is used for resuming syscalls interrupted by signals, but the updated syscall number (in scno) was not being stored in current_thread_info()->abi_syscall, causing traced syscall restarting to fail. Explicitly test for -1 in PTRACE_SET_SYSCALL and get_syscall_nr(), leaving it exposed when present, allowing tracers to skip syscalls again. Move the AEABI-only assignment of current_thread_info()->abi_syscall after the "local_restart" label to allow tracers to survive syscall restarting. Cc: Russell King Cc: Arnd Bergmann Cc: Lecopzer Chen Cc: Oleg Nesterov Cc: linux-arm-kernel@lists.infradead.org Fixes: 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall") Signed-off-by: Kees Cook --- Note that I haven't tested OABI at all, and AEABI+OABI_COMPAT doesn't work with seccomp. I booted an AEABI system under AEABI+OABI_COMPAT, but I wasn't able to test tracing... --- arch/arm/include/asm/syscall.h | 3 +++ arch/arm/kernel/entry-common.S | 5 +++-- arch/arm/kernel/ptrace.c | 5 +++-- 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h index dfeed440254a..fe4326d938c1 100644 --- a/arch/arm/include/asm/syscall.h +++ b/arch/arm/include/asm/syscall.h @@ -25,6 +25,9 @@ static inline int syscall_get_nr(struct task_struct *task, if (IS_ENABLED(CONFIG_AEABI) && !IS_ENABLED(CONFIG_OABI_COMPAT)) return task_thread_info(task)->abi_syscall; + if (task_thread_info(task)->abi_syscall == -1) + return -1; + return task_thread_info(task)->abi_syscall & __NR_SYSCALL_MASK; } diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index bcc4c9ec3aa4..08bd624e4c6f 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -246,8 +246,6 @@ ENTRY(vector_swi) bic scno, scno, #0xff000000 @ mask off SWI op-code str scno, [tsk, #TI_ABI_SYSCALL] eor scno, scno, #__NR_SYSCALL_BASE @ check OS number -#else - str scno, [tsk, #TI_ABI_SYSCALL] #endif /* * Reload the registers that may have been corrupted on entry to @@ -256,6 +254,9 @@ ENTRY(vector_swi) TRACE( ldmia sp, {r0 - r3} ) local_restart: +#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT) + str scno, [tsk, #TI_ABI_SYSCALL] @ store scno for syscall restart +#endif ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing stmdb sp!, {r4, r5} @ push fifth and sixth args diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 2d8e2516906b..fef32d73f912 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -783,8 +783,9 @@ long arch_ptrace(struct task_struct *child, long request, break; case PTRACE_SET_SYSCALL: - task_thread_info(child)->abi_syscall = data & - __NR_SYSCALL_MASK; + if (data != -1) + data &= __NR_SYSCALL_MASK; + task_thread_info(child)->abi_syscall = data; ret = 0; break;