diff options
| author | Sahitya Tummala <stummala@codeaurora.org> | 2017-06-05 16:10:31 +0530 |
|---|---|---|
| committer | Sahitya Tummala <stummala@codeaurora.org> | 2017-06-12 13:11:12 +0530 |
| commit | 33b30b124fde308d6192a55df6f176f1c36a79ce (patch) | |
| tree | bdd4e8bdfda235d6e4c9ce20f14eadf2fe215083 /fs | |
| parent | c1a2472056c800ff46e0ac21a4b67c179a570ad0 (diff) | |
fs/mbcache: fix mb_cache_lru_list corruption
With the recent 'commit d07d314e7d1d ("fs/mbcache: fix use after
free issue in mb_cache_shrink_scan()")', the ce entry is deleted
from mbcache list after ce->e_refcnt incremented under global
spinlock mb_cache_spinlock. If __mb_cache_entry_release(), is waiting
for mb_cache_spinlock at the same time, to add the same ce to
mb_cache_lru_list and if it gets the lock after mb_cache_entry_get()
deleted it, then it corrupts the list, as that element will be freed
immediately after mb_cache_entry_get(). When this list is accessed next
time for deleting/adding another ce, we see list corruption issue.
Fix this by synchronizing these two contexts with mb_cache_spinlock and
evaluating the conditions(ce->e_refcnt) in __mb_cache_entry_release()
under the global lock before adding ce to mb_cache_lru_list.
Change-Id: I3e20fb4fa163755126e30be7aeca747d74215ed2
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/mbcache.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/fs/mbcache.c b/fs/mbcache.c index ab1da987d1ae..de509271d031 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -222,8 +222,19 @@ __mb_cache_entry_release(struct mb_cache_entry *ce) * then reacquire the lock in the proper order. */ spin_lock(&mb_cache_spinlock); - if (list_empty(&ce->e_lru_list)) - list_add_tail(&ce->e_lru_list, &mb_cache_lru_list); + /* + * Evaluate the conditions under global lock mb_cache_spinlock, + * to check if mb_cache_entry_get() is running now + * and has already deleted the entry from mb_cache_lru_list + * and incremented ce->e_refcnt to prevent further additions + * to mb_cache_lru_list. + */ + if (!(ce->e_used || ce->e_queued || + atomic_read(&ce->e_refcnt))) { + if (list_empty(&ce->e_lru_list)) + list_add_tail(&ce->e_lru_list, + &mb_cache_lru_list); + } spin_unlock(&mb_cache_spinlock); } __spin_unlock_mb_cache_entry(ce); |