On Tue, 2011-06-07 at 19:19 +0200, Oleg Nesterov wrote: > On 06/03, Eric Paris wrote: > > > > The audit system previously expected arches calling to audit_syscall_exit to > > supply as arguments if the syscall was a success and what the return code was. > > Audit also provides a helper AUDITSC_RESULT which was supposed to simplify things > > by converting from negative retcodes to an audit internal magic value stating > > success or failure. This helper was wrong and could indicate that a valid > > pointer returned to userspace was a failed syscall. The fix is to fix the > > layering foolishness. We now pass audit_syscall_exit a struct pt_reg and it > > in turns calls back into arch code to collect the return value and to > > determine if the syscall was a success or failure. We also define a generic > > is_syscall_success() macro which determines success/failure based on if the > > value is < -MAX_ERRNO. This works for arches like x86 which do not use a > > separate mechanism to indicate syscall failure. > > I know nothing about audit, but the patch looks fine to me. > > > But I have a bit off-topic question, > > > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S > > index 8a445a0..b7b1f88 100644 > > --- a/arch/x86/kernel/entry_64.S > > +++ b/arch/x86/kernel/entry_64.S > > @@ -53,6 +53,7 @@ > > #include <asm/paravirt.h> > > #include <asm/ftrace.h> > > #include <asm/percpu.h> > > +#include <linux/err.h> > > > > /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ > > #include <linux/elf-em.h> > > @@ -564,17 +565,16 @@ auditsys: > > jmp system_call_fastpath > > > > /* > > - * Return fast path for syscall audit. Call audit_syscall_exit() > > + * Return fast path for syscall audit. Call __audit_syscall_exit() > > * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT > > * masked off. > > */ > > sysret_audit: > > movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */ > > - cmpq $0,%rsi /* is it < 0? */ > > - setl %al /* 1 if so, 0 if not */ > > + cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */ > > + setbe %al /* 1 if so, 0 if not */ > > movzbl %al,%edi /* zero-extend that into %edi */ > > - inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */ > > - call audit_syscall_exit > > + call __audit_syscall_exit > > With or without this patch, can't we call audit_syscall_exit() twice > if there is something else in _TIF_WORK_SYSCALL_EXIT mask apart from > SYSCALL_AUDIT ? First time it is called from asm, then from > syscall_trace_leave(), no? > > For example. The task has TIF_SYSCALL_AUDIT and nothing else, it does > system_call->auditsys->system_call_fastpath. What if it gets, say, > TIF_SYSCALL_TRACE before ret_from_sys_call? No harm is done calling twice. The first call will do the real work and cleanup. It will set a flag in the audit data that the work has been done (in_syscall == 0) thus the second call will then not do any real work and won't have anything to clean up. -Eric
