On Fri, 24 Oct 2014, Thomas Gleixner wrote: > On Sun, 12 Oct 2014, Qiaowei Ren wrote: > > +int mpx_enable_management(struct task_struct *tsk) > > +{ > > + struct mm_struct *mm = tsk->mm; > > + void __user *bd_base = MPX_INVALID_BOUNDS_DIR; > > What's the point of initializing bd_base here. I had to look twice to > figure out that it gets overwritten by task_get_bounds_dir() > > > @@ -285,6 +285,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) > > struct xsave_struct *xsave_buf; > > struct task_struct *tsk = current; > > siginfo_t info; > > + int ret = 0; > > > > prev_state = exception_enter(); > > if (notify_die(DIE_TRAP, "bounds", regs, error_code, > > @@ -312,8 +313,35 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) > > */ > > switch (status & MPX_BNDSTA_ERROR_CODE) { > > case 2: /* Bound directory has invalid entry. */ > > - if (do_mpx_bt_fault(xsave_buf)) > > + down_write(¤t->mm->mmap_sem); > > The handling of mm->mmap_sem here is horrible. The only reason why you > want to hold mmap_sem write locked in the first place is that you want > to cover the allocation and the mm->bd_addr check. > > I think it's wrong to tie this to mmap_sem in the first place. If MPX > is enabled then you should have mm->bd_addr and an explicit mutex to > protect it. > > So the logic would look like this: > > mutex_lock(&mm->bd_mutex); > if (!kernel_managed(mm)) > do_trap(); > else if (do_mpx_bt_fault()) > force_sig(); > mutex_unlock(&mm->bd_mutex); > > No tricks with mmap_sem, no special return value handling. Straight > forward code instead of a convoluted and error prone mess. After thinking about the deallocation issue, this would be mm->bd_sem. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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