From 6bde16f7dc4a43d85e488f25ad679abfd24e72d1 Mon Sep 17 00:00:00 2001 From: Susant Palai Date: Sun, 26 Apr 2015 23:49:56 +0530 Subject: dht: tackle thread race in dht_getxattr_cbk problem: 1. When two threads execute in parallel in dht_getxattr_cbk it may so happen that, both may find local->xattr to be NULL. As a result dht_aggregate_xattr may not get executed. 2. In dht_getxattr_cbk, thread1 thread2 T1 this_call_cnt = 2 -1 T2 this_call_cnt = 1 - 1 T3 fills local_xattr T4 DHT_STACK_UNWIND -> local_wipe T5 tries to dereference local which is already freed, leading to crash. Solution: for problem1: Execute critical section inside frame lock to resolve race. for problem2: Calculate this_call_count just before out section. Change-Id: I9827ac8fafebb0c733a4e4f3c710b752f1cd45fa BUG: 1215592 Signed-off-by: Susant Palai Reviewed-on: http://review.gluster.org/10389 Reviewed-by: Anuradha Talur Reviewed-by: N Balachandran Reviewed-by: Kotresh HR Tested-by: NetBSD Build System Tested-by: Gluster Build System Reviewed-by: Shyamsundar Ranganathan --- xlators/cluster/dht/src/dht-common.c | 41 +++++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/xlators/cluster/dht/src/dht-common.c b/xlators/cluster/dht/src/dht-common.c index 31270c8b8bc..12a283bd991 100644 --- a/xlators/cluster/dht/src/dht-common.c +++ b/xlators/cluster/dht/src/dht-common.c @@ -2767,29 +2767,36 @@ dht_getxattr_cbk (call_frame_t *frame, void *cookie, xlator_t *this, conf = this->private; local = frame->local; - this_call_cnt = dht_frame_return (frame); + LOCK (&frame->lock); + { + if (!xattr || (op_ret == -1)) { + local->op_ret = op_ret; + goto unlock; + } - if (!xattr || (op_ret == -1)) { - local->op_ret = op_ret; - goto out; - } + if (dict_get (xattr, conf->xattr_name)) { + dict_del (xattr, conf->xattr_name); + } - if (dict_get (xattr, conf->xattr_name)) { - dict_del (xattr, conf->xattr_name); - } + if (frame->root->pid >= 0) { + GF_REMOVE_INTERNAL_XATTR + ("trusted.glusterfs.quota*", xattr); + GF_REMOVE_INTERNAL_XATTR("trusted.pgfid*", xattr); + } - if (frame->root->pid >= 0 ) { - GF_REMOVE_INTERNAL_XATTR("trusted.glusterfs.quota*", xattr); - GF_REMOVE_INTERNAL_XATTR("trusted.pgfid*", xattr); - } + local->op_ret = 0; - local->op_ret = 0; + if (!local->xattr) { + local->xattr = dict_copy_with_ref (xattr, NULL); + } else { + dht_aggregate_xattr (local->xattr, xattr); + } - if (!local->xattr) { - local->xattr = dict_copy_with_ref (xattr, NULL); - } else { - dht_aggregate_xattr (local->xattr, xattr); } +unlock: + UNLOCK (&frame->lock); + + this_call_cnt = dht_frame_return (frame); out: if (is_last_call (this_call_cnt)) { DHT_STACK_UNWIND (getxattr, frame, local->op_ret, op_errno, -- cgit