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BUG/MEDIUM: lists: Lock the element while we check if it is in a list.

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In MT_LIST_ADDQ() and MT_LIST_ADD() we can't just check if the element is
already in a list, because there's a small race condition, it could be added
between the time we checked, and the time we actually set its next and prev.
So we have to lock it first.

This should be backported to 2.1.
This commit is contained in:
Olivier Houchard 2020-06-29 19:52:01 +02:00
parent f21695bd8b
commit 347bbf79d2
1 changed files with 34 additions and 6 deletions
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40
include/haproxy/list.h
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@ -230,8 +230,8 @@
int _ret = 0; \
struct mt_list *lh = (_lh), *el = (_el); \
while (1) { \
struct mt_list *n; \
struct mt_list *p; \
struct mt_list *n, *n2; \
struct mt_list *p, *p2; \
n = _HA_ATOMIC_XCHG(&(lh)->next, MT_LIST_BUSY); \
if (n == MT_LIST_BUSY) \
continue; \
@ -241,9 +241,23 @@
__ha_barrier_store(); \
continue; \
} \
if ((el)->next != (el) || (el)->prev != (el)) { \
n2 = _HA_ATOMIC_XCHG(&(el)->next, MT_LIST_BUSY); \
if (n2 != (el)) { \
(n)->prev = p; \
(lh)->next = n; \
(el)->next = n2; \
if (n2 == MT_LIST_BUSY) \
continue; \
break; \
} \
p2 = _HA_ATOMIC_XCHG(&(el)->prev, MT_LIST_BUSY); \
if (p2 != (el)) { \
n->prev = p; \
(lh)->next = n; \
(el)->next = n2; \
(el)->prev = p2; \
if (p2 == MT_LIST_BUSY) \
continue; \
break; \
} \
(el)->next = n; \
@ -269,8 +283,8 @@
int _ret = 0; \
struct mt_list *lh = (_lh), *el = (_el); \
while (1) { \
struct mt_list *n; \
struct mt_list *p; \
struct mt_list *n, *n2; \
struct mt_list *p, *p2; \
p = _HA_ATOMIC_XCHG(&(lh)->prev, MT_LIST_BUSY); \
if (p == MT_LIST_BUSY) \
continue; \
@ -280,9 +294,23 @@
__ha_barrier_store(); \
continue; \
} \
if ((el)->next != (el) || (el)->prev != (el)) { \
n2 = _HA_ATOMIC_XCHG(&(el)->next, MT_LIST_BUSY); \
if (n2 != (el)) { \
p->next = n; \
(lh)->prev = p; \
(el)->next = n2; \
if (n2 == MT_LIST_BUSY) \
continue; \
break; \
} \
p2 = _HA_ATOMIC_XCHG(&(el)->prev, MT_LIST_BUSY); \
if (p2 != (el)) { \
p->next = n; \
(lh)->prev = p; \
(el)->next = n2; \
(el)->prev = p2; \
if (p2 == MT_LIST_BUSY) \
continue; \
break; \
} \
(el)->next = n; \