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Fix infinite loop in dbRandomKey().

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Thanks to @kevinmcgehee for signaling the issue and reasoning about the
consequences and potential fixes.

Issue #5015.
This commit is contained in:
antirez 2018-06-14 18:08:05 +02:00
parent 1e92fde3d3
commit d6e8fe77af
1 changed files with 13 additions and 0 deletions
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13
src/db.c
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@ -223,6 +223,8 @@ int dbExists(redisDb *db, robj *key) {
* The function makes sure to return keys not already expired. */
robj *dbRandomKey(redisDb *db) {
dictEntry *de;
int maxtries = 100;
int allvolatile = dictSize(db->dict) == dictSize(db->expires);
while(1) {
sds key;
@ -234,6 +236,17 @@ robj *dbRandomKey(redisDb *db) {
key = dictGetKey(de);
keyobj = createStringObject(key,sdslen(key));
if (dictFind(db->expires,key)) {
if (allvolatile && server.masterhost && --maxtries == 0) {
/* If the DB is composed only of keys with an expire set,
* it could happen that all the keys are already logically
* expired in the slave, so the function cannot stop because
* expireIfNeeded() is false, nor it can stop because
* dictGetRandomKey() returns NULL (there are keys to return).
* To prevent the infinite loop we do some tries, but if there
* are the conditions for an infinite loop, eventually we
* return a key name that may be already expired. */
return keyobj;
}
if (expireIfNeeded(db,keyobj)) {
decrRefCount(keyobj);
continue; /* search for another key. This expired. */