diff options
author | Alistair Popple <apopple@nvidia.com> | 2022-04-21 16:36:10 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-04-21 20:01:10 -0700 |
commit | 319561669a59d8e9206ab311ae5433ef92fd79d1 (patch) | |
tree | 2a8bed66dc2b058d47b6461ffefd8c9055087ba7 /mm/mmu_notifier.c | |
parent | ecc04463d1a36f88baa750d45dfb02c364e1fdb1 (diff) |
mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()
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>
Diffstat (limited to 'mm/mmu_notifier.c')
-rw-r--r-- | mm/mmu_notifier.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index 459d195d2ff6..f45ff1b7626a 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -1036,6 +1036,18 @@ int mmu_interval_notifier_insert_locked( } EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked); +static bool +mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions, + unsigned long seq) +{ + bool ret; + + spin_lock(&subscriptions->lock); + ret = subscriptions->invalidate_seq != seq; + spin_unlock(&subscriptions->lock); + return ret; +} + /** * mmu_interval_notifier_remove - Remove a interval notifier * @interval_sub: Interval subscription to unregister @@ -1083,7 +1095,7 @@ void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub) lock_map_release(&__mmu_notifier_invalidate_range_start_map); if (seq) wait_event(subscriptions->wq, - READ_ONCE(subscriptions->invalidate_seq) != seq); + mmu_interval_seq_released(subscriptions, seq)); /* pairs with mmgrab in mmu_interval_notifier_insert() */ mmdrop(mm); |