From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga07.intel.com ([134.134.136.100]:46313 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043AbdJTIQM (ORCPT ); Fri, 20 Oct 2017 04:16:12 -0400 From: Elena Reshetova To: axboe@kernel.dk Cc: james.bottomley@hansenpartnership.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-btrfs@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, fujita.tomonori@lab.ntt.co.jp, mingo@redhat.com, clm@fb.com, jbacik@fb.com, dsterba@suse.com, keescook@chromium.org, Elena Reshetova Subject: [PATCH 1/6] block: convert bio.__bi_cnt from atomic_t to refcount_t Date: Fri, 20 Oct 2017 11:15:57 +0300 Message-Id: <1508487362-26663-2-git-send-email-elena.reshetova@intel.com> In-Reply-To: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> References: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable bio.__bi_cnt is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova --- block/bio.c | 6 +++--- fs/btrfs/volumes.c | 2 +- include/linux/bio.h | 4 ++-- include/linux/blk_types.h | 3 ++- 4 files changed, 8 insertions(+), 7 deletions(-) diff --git a/block/bio.c b/block/bio.c index 101c2a9..58edc1b 100644 --- a/block/bio.c +++ b/block/bio.c @@ -279,7 +279,7 @@ void bio_init(struct bio *bio, struct bio_vec *table, { memset(bio, 0, sizeof(*bio)); atomic_set(&bio->__bi_remaining, 1); - atomic_set(&bio->__bi_cnt, 1); + refcount_set(&bio->__bi_cnt, 1); bio->bi_io_vec = table; bio->bi_max_vecs = max_vecs; @@ -557,12 +557,12 @@ void bio_put(struct bio *bio) if (!bio_flagged(bio, BIO_REFFED)) bio_free(bio); else { - BIO_BUG_ON(!atomic_read(&bio->__bi_cnt)); + BIO_BUG_ON(!refcount_read(&bio->__bi_cnt)); /* * last put frees it */ - if (atomic_dec_and_test(&bio->__bi_cnt)) + if (refcount_dec_and_test(&bio->__bi_cnt)) bio_free(bio); } } diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index b397375..11812ee 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -450,7 +450,7 @@ static noinline void run_scheduled_bios(struct btrfs_device *device) waitqueue_active(&fs_info->async_submit_wait)) wake_up(&fs_info->async_submit_wait); - BUG_ON(atomic_read(&cur->__bi_cnt) == 0); + BUG_ON(refcount_read(&cur->__bi_cnt) == 0); /* * if we're doing the sync list, record that our diff --git a/include/linux/bio.h b/include/linux/bio.h index 275c91c..0fa4dd2 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -253,7 +253,7 @@ static inline void bio_get(struct bio *bio) { bio->bi_flags |= (1 << BIO_REFFED); smp_mb__before_atomic(); - atomic_inc(&bio->__bi_cnt); + refcount_inc(&bio->__bi_cnt); } static inline void bio_cnt_set(struct bio *bio, unsigned int count) @@ -262,7 +262,7 @@ static inline void bio_cnt_set(struct bio *bio, unsigned int count) bio->bi_flags |= (1 << BIO_REFFED); smp_mb__before_atomic(); } - atomic_set(&bio->__bi_cnt, count); + refcount_set(&bio->__bi_cnt, count); } static inline bool bio_flagged(struct bio *bio, unsigned int bit) diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index a2d2aa7..1ec370e 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -7,6 +7,7 @@ #include #include +#include struct bio_set; struct bio; @@ -104,7 +105,7 @@ struct bio { unsigned short bi_max_vecs; /* max bvl_vecs we can hold */ - atomic_t __bi_cnt; /* pin count */ + refcount_t __bi_cnt; /* pin count */ struct bio_vec *bi_io_vec; /* the actual vec list */ -- 2.7.4