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author | Tejun Heo <tj@kernel.org> | 2018-03-14 22:45:10 +0300 |
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committer | Jason Gunthorpe <jgg@mellanox.com> | 2018-03-16 00:38:19 +0300 |
commit | 95da6e96f1e74e6ddfb347f7a8310f419bb47bf7 (patch) | |
tree | b177c6ac11105639dc26f2c2d50170b04f4d8681 /drivers/infiniband/sw/rxe/rxe_verbs.c | |
parent | 561e5d48968be22fc71af6a0e13af6edae595dbe (diff) | |
download | linux-95da6e96f1e74e6ddfb347f7a8310f419bb47bf7.tar.xz |
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>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'drivers/infiniband/sw/rxe/rxe_verbs.c')
0 files changed, 0 insertions, 0 deletions