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Commitd303849

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Don't leak compiled regex(es) when an ispell cache entry is dropped.
The text search cache mechanisms assume that we can clean upan invalidated dictionary cache entry simply by resetting theassociated long-lived memory context. However, that does not workfor ispell affixes that make use of regular expressions, becausethe regex library deals in plain old malloc. Hence, we leakedcompiled regex(es) any time we dropped such a cache entry. Thatcould quickly add up, since even a fairly trivial regex can use uptens of kB, and a large one can eat megabytes. Add a memory contextcallback to ensure that a regex gets freed when its owning cacheentry is cleared.Found via valgrind testing.This problem is ancient, so back-patch to all supported branches.Discussion:https://postgr.es/m/3816764.1616104288@sss.pgh.pa.us
1 parent415ffdc commitd303849

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2 files changed

+41
-4
lines changed

2 files changed

+41
-4
lines changed

‎src/backend/tsearch/spell.c

Lines changed: 29 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -654,6 +654,17 @@ FindWord(IspellDict *Conf, const char *word, const char *affixflag, int flag)
654654
return0;
655655
}
656656

657+
/*
658+
* Context reset/delete callback for a regular expression used in an affix
659+
*/
660+
staticvoid
661+
regex_affix_deletion_callback(void*arg)
662+
{
663+
aff_regex_struct*pregex= (aff_regex_struct*)arg;
664+
665+
pg_regfree(&(pregex->regex));
666+
}
667+
657668
/*
658669
* Adds a new affix rule to the Affix field.
659670
*
@@ -716,6 +727,7 @@ NIAddAffix(IspellDict *Conf, const char *flag, char flagflags, const char *mask,
716727
interr;
717728
pg_wchar*wmask;
718729
char*tmask;
730+
aff_regex_struct*pregex;
719731

720732
Affix->issimple=0;
721733
Affix->isregis=0;
@@ -729,18 +741,32 @@ NIAddAffix(IspellDict *Conf, const char *flag, char flagflags, const char *mask,
729741
wmask= (pg_wchar*)tmpalloc((masklen+1)*sizeof(pg_wchar));
730742
wmasklen=pg_mb2wchar_with_len(tmask,wmask,masklen);
731743

732-
err=pg_regcomp(&(Affix->reg.regex),wmask,wmasklen,
744+
/*
745+
* The regex engine stores its stuff using malloc not palloc, so we
746+
* must arrange to explicitly clean up the regex when the dictionary's
747+
* context is cleared. That means the regex_t has to stay in a fixed
748+
* location within the context; we can't keep it directly in the AFFIX
749+
* struct, since we may sort and resize the array of AFFIXes.
750+
*/
751+
Affix->reg.pregex=pregex=palloc(sizeof(aff_regex_struct));
752+
753+
err=pg_regcomp(&(pregex->regex),wmask,wmasklen,
733754
REG_ADVANCED |REG_NOSUB,
734755
DEFAULT_COLLATION_OID);
735756
if (err)
736757
{
737758
charerrstr[100];
738759

739-
pg_regerror(err,&(Affix->reg.regex),errstr,sizeof(errstr));
760+
pg_regerror(err,&(pregex->regex),errstr,sizeof(errstr));
740761
ereport(ERROR,
741762
(errcode(ERRCODE_INVALID_REGULAR_EXPRESSION),
742763
errmsg("invalid regular expression: %s",errstr)));
743764
}
765+
766+
pregex->mcallback.func=regex_affix_deletion_callback;
767+
pregex->mcallback.arg= (void*)pregex;
768+
MemoryContextRegisterResetCallback(CurrentMemoryContext,
769+
&pregex->mcallback);
744770
}
745771

746772
Affix->flagflags=flagflags;
@@ -2133,7 +2159,7 @@ CheckAffix(const char *word, size_t len, AFFIX *Affix, int flagflags, char *neww
21332159
data= (pg_wchar*)palloc((newword_len+1)*sizeof(pg_wchar));
21342160
data_len=pg_mb2wchar_with_len(newword,data,newword_len);
21352161

2136-
if (pg_regexec(&(Affix->reg.regex),data,data_len,
2162+
if (pg_regexec(&(Affix->reg.pregex->regex),data,data_len,
21372163
0,NULL,0,NULL,0)==REG_OKAY)
21382164
{
21392165
pfree(data);

‎src/include/tsearch/dicts/spell.h

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -81,6 +81,17 @@ typedef struct spell_struct
8181

8282
#defineSPELLHDRSZ(offsetof(SPELL, word))
8383

84+
/*
85+
* If an affix uses a regex, we have to store that separately in a struct
86+
* that won't move around when arrays of affixes are enlarged or sorted.
87+
* This is so that it can be found to be cleaned up at context destruction.
88+
*/
89+
typedefstructaff_regex_struct
90+
{
91+
regex_tregex;
92+
MemoryContextCallbackmcallback;
93+
}aff_regex_struct;
94+
8495
/*
8596
* Represents an entry in an affix list.
8697
*/
@@ -97,7 +108,7 @@ typedef struct aff_struct
97108
char*repl;
98109
union
99110
{
100-
regex_tregex;
111+
aff_regex_struct*pregex;
101112
Regisregis;
102113
}reg;
103114
}AFFIX;

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