lkml.org 
[lkml]   [2022]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.15 082/124] mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()
    Date
    From: Alistair Popple <apopple@nvidia.com>

    commit 319561669a59d8e9206ab311ae5433ef92fd79d1 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    mm/mmu_notifier.c | 14 +++++++++++++-
    1 file changed, 13 insertions(+), 1 deletion(-)

    --- 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
    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);

    \
     
     \ /
      Last update: 2022-04-26 11:18    [W:2.416 / U:0.048 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site