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    Subject[PATCH 5.15 105/128] mm/damon/dbgfs: protect targets destructions with kdamond_lock
    Date
    From: SeongJae Park <sj@kernel.org>

    commit 34796417964b8d0aef45a99cf6c2d20cebe33733 upstream.

    DAMON debugfs interface iterates current monitoring targets in
    'dbgfs_target_ids_read()' while holding the corresponding
    'kdamond_lock'. However, it also destructs the monitoring targets in
    'dbgfs_before_terminate()' without holding the lock. This can result in
    a use_after_free bug. This commit avoids the race by protecting the
    destruction with the corresponding 'kdamond_lock'.

    Link: https://lkml.kernel.org/r/20211221094447.2241-1-sj@kernel.org
    Reported-by: Sangwoo Bae <sangwoob@amazon.com>
    Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
    Signed-off-by: SeongJae Park <sj@kernel.org>
    Cc: <stable@vger.kernel.org> [5.15.x]
    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/damon/dbgfs.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/mm/damon/dbgfs.c
    +++ b/mm/damon/dbgfs.c
    @@ -309,10 +309,12 @@ static int dbgfs_before_terminate(struct
    if (!targetid_is_pid(ctx))
    return 0;

    + mutex_lock(&ctx->kdamond_lock);
    damon_for_each_target_safe(t, next, ctx) {
    put_pid((struct pid *)t->id);
    damon_destroy_target(t);
    }
    + mutex_unlock(&ctx->kdamond_lock);
    return 0;
    }


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