From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from s3.sipsolutions.net ([2a01:4f8:191:4433::2] helo=sipsolutions.net) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lHTwN-005Va5-Na for linux-um@lists.infradead.org; Wed, 03 Mar 2021 16:01:38 +0000 From: Benjamin Berg Subject: [PATCH 22/27] um: Add stub side of SECCOMP/futex based process handling Date: Wed, 3 Mar 2021 16:55:18 +0100 Message-Id: <20210303155523.124277-23-benjamin@sipsolutions.net> In-Reply-To: <20210303155523.124277-1-benjamin@sipsolutions.net> References: <20210303155523.124277-1-benjamin@sipsolutions.net> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: linux-um@lists.infradead.org Cc: Benjamin Berg , Johannes Berg This adds the stub side for the new seccomp process management code. In this case we do register save/restore through the signal handler mcontext. For the FS_BASE/GS_BASE register we need special handling. Co-authored-by: Johannes Berg Signed-off-by: Benjamin Berg --- arch/um/include/shared/skas/stub-data.h | 15 +++++++ arch/um/kernel/skas/clone.c | 25 ++++++++++++ arch/um/kernel/skas/stub.c | 53 +++++++++++++++++++++++++ arch/x86/um/shared/sysdep/stub-data.h | 11 +++++ arch/x86/um/shared/sysdep/stub.h | 3 ++ arch/x86/um/shared/sysdep/stub_32.h | 5 +++ arch/x86/um/shared/sysdep/stub_64.h | 10 +++++ 7 files changed, 122 insertions(+) create mode 100644 arch/x86/um/shared/sysdep/stub-data.h diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h index efa78bc359cb..e130c428cda9 100644 --- a/arch/um/include/shared/skas/stub-data.h +++ b/arch/um/include/shared/skas/stub-data.h @@ -8,8 +8,13 @@ #ifndef __STUB_DATA_H #define __STUB_DATA_H +#include #include #include +#include + +#define FUTEX_IN_CHILD 0 +#define FUTEX_IN_KERN 1 #define STUB_NEXT_SYSCALL(s) \ ((struct stub_syscall *) (((unsigned long) s) + (s)->cmd_len)) @@ -32,6 +37,16 @@ struct stub_data { unsigned char syscall_data[UM_KERN_PAGE_SIZE - MINSIGSTKSZ - 128] __aligned(16); + /* data shared with signal handler (only used in seccomp mode) */ + short restart_wait; + unsigned int futex; + int signal; + unsigned short si_offset; + unsigned short mctx_offset; + + /* seccomp architecture specific state restore */ + struct stub_data_arch arch_data; + /* Stack for our signal handlers and for calling into . */ unsigned char sigstack[MINSIGSTKSZ + 32] __aligned(16); }; diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c index a680d80b3870..d6e0742c77fd 100644 --- a/arch/um/kernel/skas/clone.c +++ b/arch/um/kernel/skas/clone.c @@ -49,3 +49,28 @@ stub_clone_handler(void) done: trap_myself(); } + +#ifdef CONFIG_UML_SECCOMP +void __attribute__ ((__section__ (".__syscall_stub"))) +stub_clone_handler_seccomp(void) +{ + int stack; + struct stub_data *data = (void *) ((unsigned long)&stack & ~(UM_KERN_PAGE_SIZE - 1)); + long err; + + /* Use the syscall data as a temporary stack area. */ + err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, + (unsigned long) data->syscall_data + + sizeof(data->syscall_data) - + sizeof(void *)); + if (err) { + data->err = err; + goto done; + } + + remap_stack_and_trap(); + + done: + trap_myself(); +} +#endif diff --git a/arch/um/kernel/skas/stub.c b/arch/um/kernel/skas/stub.c index 5d1bcc883866..4bf32fdf4599 100644 --- a/arch/um/kernel/skas/stub.c +++ b/arch/um/kernel/skas/stub.c @@ -5,6 +5,13 @@ #include +#ifdef CONFIG_UML_SECCOMP +#include +#include + +#define CATCH_EINTR(expr) while ((res = (expr)) && (res == -EINTR)) +#endif + static __always_inline int syscall_handler(struct stub_data *d) { @@ -50,3 +57,49 @@ stub_syscall_handler(void) trap_myself(); } + +#ifdef CONFIG_UML_SECCOMP +void __attribute__ ((__section__ (".__syscall_stub"))) +stub_signal_interrupt(int sig, siginfo_t *info, void *p) +{ + int stack; + struct stub_data *d = (void *) ((unsigned long)&stack & ~(UM_KERN_PAGE_SIZE - 1)); + ucontext_t *uc = p; + long res; + + d->signal = sig; + d->si_offset = (unsigned long)info - (unsigned long)&d->sigstack[0]; + d->mctx_offset = (unsigned long)&uc->uc_mcontext - (unsigned long)&d->sigstack[0]; + +restart_wait: + d->futex = FUTEX_IN_KERN; + CATCH_EINTR(stub_syscall3(__NR_futex, (unsigned long)&d->futex, + FUTEX_WAKE, 1)); + do { + res = stub_syscall4(__NR_futex, (unsigned long)&d->futex, + FUTEX_WAIT, FUTEX_IN_KERN, 0); + } while (res == -EINTR || d->futex == FUTEX_IN_KERN); + + if (res < 0 && res != -EAGAIN) + stub_syscall2(__NR_kill, 0, SIGKILL); + + /* Try running queued syscalls. */ + if (syscall_handler(d) < 0 || d->restart_wait) { + /* Report SIGTRAP if we restart. */ + d->signal = SIGTRAP; + d->restart_wait = 0; + goto restart_wait; + } + + /* Restore arch dependent state that is not part of the mcontext */ + stub_seccomp_restore_state(&d->arch_data); + + /* Return so that the host modified mcontext is restored. */ +} + +void __attribute__ ((__section__ (".__syscall_stub"))) +stub_signal_restorer(void) +{ + stub_syscall0(__NR_rt_sigreturn); +} +#endif diff --git a/arch/x86/um/shared/sysdep/stub-data.h b/arch/x86/um/shared/sysdep/stub-data.h new file mode 100644 index 000000000000..2e71b48ebb1f --- /dev/null +++ b/arch/x86/um/shared/sysdep/stub-data.h @@ -0,0 +1,11 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifdef __i386__ +struct stub_data_arch { }; +#else +struct stub_data_arch { + int sync; + unsigned long fs_base; + unsigned long gs_base; +}; +#endif + diff --git a/arch/x86/um/shared/sysdep/stub.h b/arch/x86/um/shared/sysdep/stub.h index 579681d12158..eb2e3a24d40b 100644 --- a/arch/x86/um/shared/sysdep/stub.h +++ b/arch/x86/um/shared/sysdep/stub.h @@ -14,3 +14,6 @@ extern void stub_segv_handler(int, siginfo_t *, void *); extern void stub_syscall_handler(void); extern void stub_clone_handler(void); +extern void stub_signal_interrupt(int, siginfo_t *, void *); +extern void stub_signal_restorer(void); +extern void stub_clone_handler_seccomp(void); diff --git a/arch/x86/um/shared/sysdep/stub_32.h b/arch/x86/um/shared/sysdep/stub_32.h index 3fb8559fe994..62aa7597576a 100644 --- a/arch/x86/um/shared/sysdep/stub_32.h +++ b/arch/x86/um/shared/sysdep/stub_32.h @@ -130,4 +130,9 @@ static __always_inline void remap_stack_and_trap(void) "memory"); } +static __always_inline void stub_seccomp_restore_state(struct stub_data_arch *arch) +{ + /* No extra arch specific restore */ +} + #endif diff --git a/arch/x86/um/shared/sysdep/stub_64.h b/arch/x86/um/shared/sysdep/stub_64.h index c41ae0462c8f..69f9aeca8cee 100644 --- a/arch/x86/um/shared/sysdep/stub_64.h +++ b/arch/x86/um/shared/sysdep/stub_64.h @@ -8,6 +8,7 @@ #include #include +#include #define STUB_MMAP_NR __NR_mmap #define MMAP_OFFSET(o) (o) @@ -125,4 +126,13 @@ static __always_inline void remap_stack_and_trap(void) __syscall_clobber, "r10", "r8", "r9"); } +static __always_inline void stub_seccomp_restore_state(struct stub_data_arch *arch) +{ + /* TODO: Use _writefsbase_u64/_writegsbase_u64 when possible */ + if (arch->sync & 0x1) + stub_syscall2(__NR_arch_prctl, ARCH_SET_FS, arch->fs_base); + if (arch->sync & 0x2) + stub_syscall2(__NR_arch_prctl, ARCH_SET_GS, arch->gs_base); +} + #endif -- 2.29.2 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um