On Fri, 11 May 2007 00:36:25 +0200 "Rafael J. Wysocki" <[EMAIL PROTECTED]> wrote:
> The reading of PF_BORROWED_MM in is_user_space() without task_lock() is racy. > Fix it. > > Signed-off-by: Rafael J. Wysocki <[EMAIL PROTECTED]> > Acked-by: Pavel Machek <[EMAIL PROTECTED]> > --- > kernel/power/process.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > Index: linux-2.6/kernel/power/process.c > =================================================================== > --- linux-2.6.orig/kernel/power/process.c 2007-05-10 21:44:23.000000000 > +0200 > +++ linux-2.6/kernel/power/process.c 2007-05-10 21:44:28.000000000 +0200 > @@ -8,6 +8,7 @@ > > #undef DEBUG > > +#include <linux/sched.h> > #include <linux/interrupt.h> > #include <linux/suspend.h> > #include <linux/module.h> > @@ -88,7 +89,12 @@ static void cancel_freezing(struct task_ > > static inline int is_user_space(struct task_struct *p) > { > - return p->mm && !(p->flags & PF_BORROWED_MM); > + int ret; > + > + task_lock(p); > + ret = p->mm && !(p->flags & PF_BORROWED_MM); > + task_unlock(p); > + return ret; > } The whole function is racy, isn't it? I mean, the condition which it is testing can go from true->false or false->true at any instant after this function returns its now-wrong value. iow, callers of this function need to to something to prevent the expression `p->mm && !(p->flags & PF_BORROWED_MM);' from changing value _anyway_. In which case the new locking is not needed? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/