From: Gerald Schaefer Date: Wed, 12 May 2010 07:32:12 +0000 (+0200) Subject: ptrace: fix return value of do_syscall_trace_enter() X-Git-Tag: firefly_0821_release~10186^2~1611 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fa157eec79e78a875790df6faf53b3501c33a462;p=firefly-linux-kernel-4.4.55.git ptrace: fix return value of do_syscall_trace_enter() commit 545c174d1f093a462b4bb9131b23d5ea72a600e1 upstream. strace may change the system call number, so regs->gprs[2] must not be read before tracehook_report_syscall_entry(). This fixes a bug where "strace -f" will hang after a vfork(). Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c index 653c6a178740..08f883842e21 100644 --- a/arch/s390/kernel/ptrace.c +++ b/arch/s390/kernel/ptrace.c @@ -632,7 +632,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request, asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) { - long ret; + long ret = 0; /* Do the secure computing check first. */ secure_computing(regs->gprs[2]); @@ -641,7 +641,6 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) * The sysc_tracesys code in entry.S stored the system * call number to gprs[2]. */ - ret = regs->gprs[2]; if (test_thread_flag(TIF_SYSCALL_TRACE) && (tracehook_report_syscall_entry(regs) || regs->gprs[2] >= NR_syscalls)) { @@ -663,7 +662,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) regs->gprs[2], regs->orig_gpr2, regs->gprs[3], regs->gprs[4], regs->gprs[5]); - return ret; + return ret ?: regs->gprs[2]; } asmlinkage void do_syscall_trace_exit(struct pt_regs *regs)