From: Jeff Dike <jdike@addtoit.com> From: Bodo Stroesser <bstroesser@fujitsu-siemens.com> My older patch, that sets TIF_SIGPENDING after an ptrace-interception in syscall_trace() is wrong. Some syscalls want to be called without any signal pending. If a signal is pending on syscall-entry, they immediately return with -ERESTARTNOINTR. Thus, on return to user, the pending signals can be processed and the kernel will lower eip by 2 to have the syscall restarted after that. Since my change sets TIF_SIGPENDING on the entry and exit interception, stracing such a syscall looped! Try "strace ls" to see what happens. Fix: set TIF_SIGPENDING on the exit interception only. This avoids the loop and is enough for security. Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com> Signed-off-by: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- 25-akpm/arch/um/kernel/ptrace.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff -puN arch/um/kernel/ptrace.c~uml-fix-setting-of-tif_sigpending arch/um/kernel/ptrace.c --- 25/arch/um/kernel/ptrace.c~uml-fix-setting-of-tif_sigpending Fri Dec 3 13:50:37 2004 +++ 25-akpm/arch/um/kernel/ptrace.c Fri Dec 3 13:50:37 2004 @@ -330,8 +330,8 @@ void syscall_trace(union uml_pt_regs *re tracesysgood = (current->ptrace & PT_TRACESYSGOOD) && !is_singlestep; ptrace_notify(SIGTRAP | (tracesysgood ? 0x80 : 0)); - /* force do_signal() --> is_syscall() */ - set_thread_flag(TIF_SIGPENDING); + if (entryexit) /* force do_signal() --> is_syscall() */ + set_thread_flag(TIF_SIGPENDING); /* this isn't the same as continuing with a signal, but it will do * for normal use. strace only continues with a signal if the _