From 5bfce0b74fbd5d53089bb866919d685c47edad9e Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 25 Jul 2019 14:16:45 +0100 Subject: [PATCH] linux-user: Make sigaltstack stacks per-thread The alternate signal stack set up by the sigaltstack syscall is supposed to be per-thread. We were incorrectly implementing it as process-wide. This causes problems for guest binaries that rely on this. Notably the Go runtime does, and so we were seeing crashes caused by races where two guest threads might incorrectly both execute on the same stack simultaneously. Replace the global target_sigaltstack_used with a field sigaltstack_used in the TaskState, and make all the references to the old global instead get a pointer to the TaskState and use the field. Fixes: https://bugs.launchpad.net/qemu/+bug/1696773 Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Tested-by: Laurent Vivier Reviewed-by: Laurent Vivier Message-Id: <20190725131645.19501-1-peter.maydell@linaro.org> Signed-off-by: Laurent Vivier --- linux-user/hppa/signal.c | 3 ++- linux-user/main.c | 5 +++++ linux-user/qemu.h | 2 ++ linux-user/signal-common.h | 1 - linux-user/signal.c | 35 +++++++++++++++++++---------------- 5 files changed, 28 insertions(+), 18 deletions(-) diff --git a/linux-user/hppa/signal.c b/linux-user/hppa/signal.c index b6927ee673..d1a58feeb3 100644 --- a/linux-user/hppa/signal.c +++ b/linux-user/hppa/signal.c @@ -111,10 +111,11 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, abi_ulong frame_addr, sp, haddr; struct target_rt_sigframe *frame; int i; + TaskState *ts = (TaskState *)thread_cpu->opaque; sp = get_sp_from_cpustate(env); if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { - sp = (target_sigaltstack_used.ss_sp + 0x7f) & ~0x3f; + sp = (ts->sigaltstack_used.ss_sp + 0x7f) & ~0x3f; } frame_addr = QEMU_ALIGN_UP(sp, 64); sp = frame_addr + PARISC_RT_SIGFRAME_SIZE32; diff --git a/linux-user/main.c b/linux-user/main.c index a59ae9439d..8ffc525195 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -180,6 +180,11 @@ void stop_all_tasks(void) void init_task_state(TaskState *ts) { ts->used = 1; + ts->sigaltstack_used = (struct target_sigaltstack) { + .ss_sp = 0, + .ss_size = 0, + .ss_flags = TARGET_SS_DISABLE, + }; } CPUArchState *cpu_copy(CPUArchState *env) diff --git a/linux-user/qemu.h b/linux-user/qemu.h index 4258e4162d..aac0334627 100644 --- a/linux-user/qemu.h +++ b/linux-user/qemu.h @@ -151,6 +151,8 @@ typedef struct TaskState { */ int signal_pending; + /* This thread's sigaltstack, if it has one */ + struct target_sigaltstack sigaltstack_used; } __attribute__((aligned(16))) TaskState; extern char *exec_path; diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h index 51030a9306..1df1068552 100644 --- a/linux-user/signal-common.h +++ b/linux-user/signal-common.h @@ -19,7 +19,6 @@ #ifndef SIGNAL_COMMON_H #define SIGNAL_COMMON_H -extern struct target_sigaltstack target_sigaltstack_used; int on_sig_stack(unsigned long sp); int sas_ss_flags(unsigned long sp); diff --git a/linux-user/signal.c b/linux-user/signal.c index 5cd237834d..5ca6d62b15 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -25,12 +25,6 @@ #include "trace.h" #include "signal-common.h" -struct target_sigaltstack target_sigaltstack_used = { - .ss_sp = 0, - .ss_size = 0, - .ss_flags = TARGET_SS_DISABLE, -}; - static struct target_sigaction sigact_table[TARGET_NSIG]; static void host_signal_handler(int host_signum, siginfo_t *info, @@ -251,13 +245,17 @@ void set_sigmask(const sigset_t *set) int on_sig_stack(unsigned long sp) { - return (sp - target_sigaltstack_used.ss_sp - < target_sigaltstack_used.ss_size); + TaskState *ts = (TaskState *)thread_cpu->opaque; + + return (sp - ts->sigaltstack_used.ss_sp + < ts->sigaltstack_used.ss_size); } int sas_ss_flags(unsigned long sp) { - return (target_sigaltstack_used.ss_size == 0 ? SS_DISABLE + TaskState *ts = (TaskState *)thread_cpu->opaque; + + return (ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE : on_sig_stack(sp) ? SS_ONSTACK : 0); } @@ -266,17 +264,21 @@ abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka) /* * This is the X/Open sanctioned signal stack switching. */ + TaskState *ts = (TaskState *)thread_cpu->opaque; + if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { - return target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size; + return ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size; } return sp; } void target_save_altstack(target_stack_t *uss, CPUArchState *env) { - __put_user(target_sigaltstack_used.ss_sp, &uss->ss_sp); + TaskState *ts = (TaskState *)thread_cpu->opaque; + + __put_user(ts->sigaltstack_used.ss_sp, &uss->ss_sp); __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags); - __put_user(target_sigaltstack_used.ss_size, &uss->ss_size); + __put_user(ts->sigaltstack_used.ss_size, &uss->ss_size); } /* siginfo conversion */ @@ -708,12 +710,13 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) { int ret; struct target_sigaltstack oss; + TaskState *ts = (TaskState *)thread_cpu->opaque; /* XXX: test errors */ if(uoss_addr) { - __put_user(target_sigaltstack_used.ss_sp, &oss.ss_sp); - __put_user(target_sigaltstack_used.ss_size, &oss.ss_size); + __put_user(ts->sigaltstack_used.ss_sp, &oss.ss_sp); + __put_user(ts->sigaltstack_used.ss_size, &oss.ss_size); __put_user(sas_ss_flags(sp), &oss.ss_flags); } @@ -760,8 +763,8 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) } } - target_sigaltstack_used.ss_sp = ss.ss_sp; - target_sigaltstack_used.ss_size = ss.ss_size; + ts->sigaltstack_used.ss_sp = ss.ss_sp; + ts->sigaltstack_used.ss_size = ss.ss_size; } if (uoss_addr) {