On Wed, 7 Jul 2010, Christoph Hellwig wrote: > On Wed, Jul 07, 2010 at 10:31:37AM -0700, Linus Torvalds wrote: > > On Wed, Jul 7, 2010 at 10:11 AM, Ulrich Drepper <drepper@xxxxxxxxxx> wrote: > > > > > > How does this work with old kernels which didn't initialize f_spare? > > > > Some of the compat layers (and older kernels) don't copy the f_spare > > values, so user space should clear the field before doing the system > > call, and you should be ok. > > > > There should be no actual _uninitialized_ values copied from the > > kernel. IOW, either the kernel writes zero, or it doesn't write > > anything at all. Anything else would be a security issue anyway (ie > > kernel stack data leak). Afaik, no kernel does that. > > Sometime before 2.4.0 (I posted the exact release in the previous > thread) the kernel initalized unused fields to 0xff. So if we want to > support these kernels it is an issue. 1.0 - doesn't touch spare fields 1.2.13 - doesn't touch spare fields 2.0.40 - copies spare fields from uninitialized kernel stack 2.2.26 - copies spare fields from uninitialized kernel stack 2.4 onward - zeroes spare fields Thanks, Miklos -- 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
