protocol/client: Fix double free of client fdctx destroy

This patch fixes the race between fd re-open code and fd release code,
both of which free the fd context due to a race in certain variable
checks as explained below:

1. client process (shd in the case of this BZ) sends an opendir to its
children (client xlators) which send the fop to the bricks to get a valid fd.

2. Client xlator loses connection to the brick. fdctx->remotefd is -1

3. Client re-establishes connection. After handshake, it reopens the dir
and sets fdctx->remotefd to a valid fd in client3_3_reopendir_cbk().

4. Meanwhile, shd sends a fd unref after it is done with the opendir.
This triggers a releasedir (since fd->refcount becomes 0).

5. client3_3_releasedir() sees that fdctx-->remotefd is a valid number
(i.e not -1), sets fdctx->released=1 and calls  client_fdctx_destroy()

6. As a continuation of step3, client_reopen_done() is called by
client3_3_reopendir_cbk(), which sees that fdctx->released==1 and
again calls client_fdctx_destroy().

Depending on when step-5 does GF_FREE(fdctx), we may crash at any place in
step-6 in client3_3_reopendir_cbk() when it tries to access
fdctx->{whatever}.

> Reviewed-on: https://review.gluster.org/16521
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
(cherry picked from commit 25fc74f9d1f2b1e7bab76485a99f27abadd10b7b)

Change-Id: Ia50873d11763e084e41d2a1f4d53715438e5e947
BUG: 1422352
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: https://review.gluster.org/16621
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

0 files changed, 0 insertions, 0 deletions