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author | 2018-03-14 12:10:18 -0700 | |
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committer | 2018-03-14 12:10:18 -0700 | |
commit | 74b44bbe80b4c62113ac1501482ea1ee40eb9d67 (patch) | |
tree | beed7a8028f6f71ba59cfb38074bea91a067bd41 /drivers/block | |
parent | fs/aio: Use RCU accessors for kioctx_table->table[] (diff) | |
download | linux-dev-74b44bbe80b4c62113ac1501482ea1ee40eb9d67.tar.xz linux-dev-74b44bbe80b4c62113ac1501482ea1ee40eb9d67.zip |
RDMAVT: Fix synchronization around percpu_ref
rvt_mregion uses percpu_ref for reference counting and RCU to protect
accesses from lkey_table. When a rvt_mregion needs to be freed, it
first gets unregistered from lkey_table and then rvt_check_refs() is
called to wait for in-flight usages before the rvt_mregion is freed.
rvt_check_refs() seems to have a couple issues.
* It has a fast exit path which tests percpu_ref_is_zero(). However,
a percpu_ref reading zero doesn't mean that the object can be
released. In fact, the ->release() callback might not even have
started executing yet. Proceeding with freeing can lead to
use-after-free.
* lkey_table is RCU protected but there is no RCU grace period in the
free path. percpu_ref uses RCU internally but it's sched-RCU whose
grace periods are different from regular RCU. Also, it generally
isn't a good idea to depend on internal behaviors like this.
To address the above issues, this patch removes the fast exit and adds
an explicit synchronize_rcu().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: linux-rdma@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block')
0 files changed, 0 insertions, 0 deletions