https://github.com/torvalds/linux
Revision 319561669a59d8e9206ab311ae5433ef92fd79d1 authored by Alistair Popple on 21 April 2022, 23:36:10 UTC, committed by Linus Torvalds on 22 April 2022, 03:01:10 UTC
In some cases it is possible for mmu_interval_notifier_remove() to race with mn_tree_inv_end() allowing it to return while the notifier data structure is still in use. Consider the following sequence: CPU0 - mn_tree_inv_end() CPU1 - mmu_interval_notifier_remove() ----------------------------------- ------------------------------------ spin_lock(subscriptions->lock); seq = subscriptions->invalidate_seq; spin_lock(subscriptions->lock); spin_unlock(subscriptions->lock); subscriptions->invalidate_seq++; wait_event(invalidate_seq != seq); return; interval_tree_remove(interval_sub); kfree(interval_sub); spin_unlock(subscriptions->lock); wake_up_all(); As the wait_event() condition is true it will return immediately. This can lead to use-after-free type errors if the caller frees the data structure containing the interval notifier subscription while it is still on a deferred list. Fix this by taking the appropriate lock when reading invalidate_seq to ensure proper synchronisation. I observed this whilst running stress testing during some development. You do have to be pretty unlucky, but it leads to the usual problems of use-after-free (memory corruption, kernel crash, difficult to diagnose WARN_ON, etc). Link: https://lkml.kernel.org/r/20220420043734.476348-1-apopple@nvidia.com Fixes: 99cb252f5e68 ("mm/mmu_notifier: add an interval tree notifier") Signed-off-by: Alistair Popple <apopple@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Cc: Christian König <christian.koenig@amd.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tip revision: 319561669a59d8e9206ab311ae5433ef92fd79d1 authored by Alistair Popple on 21 April 2022, 23:36:10 UTC
mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()
mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()
Tip revision: 3195616
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