On Thu, Mar 22, 2012 at 4:53 PM, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote: > On Thu, 2012-03-22 at 14:22 +0000, Al Viro wrote: >> On Wed, Mar 21, 2012 at 02:54:15PM -0400, Mimi Zohar wrote: >> > If a file is closed before it is munmapped, __fput() is called with >> > the mmap_sem taken. With IMA-appraisal enabled, this results in an >> > mmap_sem/i_mutex lockdep. ima_defer_fput() increments the f_count >> > to defer __fput() being called until after the mmap_sem is released. >> >> NAK. It's far too heavy-weight for what's a very common path. Worse, >> it causes different locking conditions on IMA and non-IMA kernels and makes >> bugs harder to spot. Rejected with extreme prejudice; please, fix your >> locking instead. > > Al, thanks for replying! I realize you are very prejudiced against IMA, > but have you taken a look at IMA-appraisal? It probably would have been > better if we used another name in order to avoid this prejudice, but > unfortunately we didn't. :( IMA-appraisal is about enforcing file > integrity. > >> BTW, you've missed several other places in mm/* doing fput(), so it wouldn't >> be enough to paper over your problem anyway. >> In current solution, deferred call can be added directly to __fput and checking if mmap_sem is locked. >> Final fput() *can* happen under mmap_sem. Period. > > I think I got that loud and clear; otherwise we wouldn't have come up > with deferring the __fput(). We have a very real problem here - writing > extended attributes requires taking the i_mutex. I'm open to any > suggestions. > > thanks, > > Mimi > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
