On Wed, 7 Aug 2024 20:25:45 +0100 Pedro Falcato <pedro.falcato@xxxxxxxxx> wrote: > On Wed, Aug 7, 2024 at 7:58 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Wed, 7 Aug 2024 18:33:35 +0100 Pedro Falcato <pedro.falcato@xxxxxxxxx> wrote: > > > > > is_madv_discard did its check wrong. MADV_ flags are not bitwise, > > > they're normal sequential numbers. So, for instance: > > > behavior & (/* ... */ | MADV_REMOVE) > > > > > > tagged both MADV_REMOVE and MADV_RANDOM (bit 0 set) as > > > discard operations. This is obviously incorrect, so use > > > a switch statement instead. > > > > Please describe the userspace-visible runtime effects of this bug? > > The kernel could erroneously block certain madvises (e.g MADV_RANDOM > or MADV_HUGEPAGE) on sealed VMAs due to them sharing bits with blocked > MADV operations (e.g REMOVE or WIPEONFORK). Thanks, I updated the changelog.
