From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41807) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b5W7K-0001Pa-JE for qemu-devel@nongnu.org; Wed, 25 May 2016 06:32:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b5W79-0003Jj-Tx for qemu-devel@nongnu.org; Wed, 25 May 2016 06:32:46 -0400 Received: from mail-lb0-x235.google.com ([2a00:1450:4010:c04::235]:35114) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b5W79-0003JN-NK for qemu-devel@nongnu.org; Wed, 25 May 2016 06:32:35 -0400 Received: by mail-lb0-x235.google.com with SMTP id ww9so14020641lbc.2 for ; Wed, 25 May 2016 03:32:35 -0700 (PDT) From: riku.voipio@linaro.org Date: Wed, 25 May 2016 13:31:58 +0300 Message-Id: <4c34cee95eec717558c1239ef4e54d0e7464272d.1464153942.git.riku.voipio@linaro.org> In-Reply-To: References: Subject: [Qemu-devel] [PULL 26/38] linux-user: Use safe_syscall for execve syscall List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Timothy E Baldwin From: Timothy E Baldwin Wrap execve() in the safe-syscall handling. Although execve() is not an interruptible syscall, it is a special case: if we allow a signal to happen before we make the host$ syscall then we will 'lose' it, because at the point of execve the process leaves QEMU's control. So we use the safe syscall wrapper to ensure that we either take the signal as a guest signal, or else it does not happen before the execve completes and makes it the other program's problem. The practical upshot is that without this SIGTERM could fail to terminate the process. Signed-off-by: Timothy Edward Baldwin Message-id: 1441497448-32489-25-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: expanded commit message to explain in more detail why this is needed, and add comment about it too] Reviewed-by: Peter Maydell Signed-off-by: Peter Maydell Signed-off-by: Riku Voipio --- linux-user/syscall.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index d9f4695..dea827f 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -703,6 +703,7 @@ safe_syscall4(pid_t, wait4, pid_t, pid, int *, status, int, options, \ struct rusage *, rusage) safe_syscall5(int, waitid, idtype_t, idtype, id_t, id, siginfo_t *, infop, \ int, options, struct rusage *, rusage) +safe_syscall3(int, execve, const char *, filename, char **, argv, char **, envp) static inline int host_to_target_sock_type(int host_type) { @@ -6179,7 +6180,17 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, if (!(p = lock_user_string(arg1))) goto execve_efault; - ret = get_errno(execve(p, argp, envp)); + /* Although execve() is not an interruptible syscall it is + * a special case where we must use the safe_syscall wrapper: + * if we allow a signal to happen before we make the host + * syscall then we will 'lose' it, because at the point of + * execve the process leaves QEMU's control. So we use the + * safe syscall wrapper to ensure that we either take the + * signal as a guest signal, or else it does not happen + * before the execve completes and makes it the other + * program's problem. + */ + ret = get_errno(safe_execve(p, argp, envp)); unlock_user(p, arg1, 0); goto execve_end; -- 2.1.4