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Commita223b9e

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Fix two low-probability memory leaks in regular expression parsing.
If pg_regcomp failed after having invoked markst/cleanst, it would leak any"struct subre" nodes it had created. (We've already detected all regexsyntax errors at that point, so the only likely causes of later failurewould be query cancel or out-of-memory.) To fix, make sure freesrnodeknows the difference between the pre-cleanst and post-cleanst cleanupprocedures. Add some documentation of this less-than-obvious point.Also, newlacon did the wrong thing with an out-of-memory failure fromrealloc(), so that the previously allocated array would be leaked.Both of these are pretty low-probability scenarios, but a bug is a bug,so patch all the way back.Per bug #10976 from Arthur O'Dwyer.
1 parentb42f09f commita223b9e

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-7
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1 file changed

+24
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‎src/backend/regex/regcomp.c‎

Lines changed: 24 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1680,8 +1680,9 @@ freesrnode(struct vars * v,/* might be NULL */
16801680
freecnfa(&sr->cnfa);
16811681
sr->flags=0;
16821682

1683-
if (v!=NULL)
1683+
if (v!=NULL&&v->treechain!=NULL)
16841684
{
1685+
/* we're still parsing, maybe we can reuse the subre */
16851686
sr->left=v->treefree;
16861687
v->treefree=sr;
16871688
}
@@ -1727,6 +1728,20 @@ numst(struct subre * t,
17271728

17281729
/*
17291730
* markst - mark tree nodes as INUSE
1731+
*
1732+
* Note: this is a great deal more subtle than it looks. During initial
1733+
* parsing of a regex, all subres are linked into the treechain list;
1734+
* discarded ones are also linked into the treefree list for possible reuse.
1735+
* After we are done creating all subres required for a regex, we run markst()
1736+
* then cleanst(), which results in discarding all subres not reachable from
1737+
* v->tree. We then clear v->treechain, indicating that subres must be found
1738+
* by descending from v->tree. This changes the behavior of freesubre(): it
1739+
* will henceforth FREE() unwanted subres rather than sticking them into the
1740+
* treefree list. (Doing that any earlier would result in dangling links in
1741+
* the treechain list.) This all means that freev() will clean up correctly
1742+
* if invoked before or after markst()+cleanst(); but it would not work if
1743+
* called partway through this state conversion, so we mustn't error out
1744+
* in or between these two functions.
17301745
*/
17311746
staticvoid
17321747
markst(structsubre*t)
@@ -1824,25 +1839,27 @@ newlacon(struct vars * v,
18241839
intpos)
18251840
{
18261841
intn;
1842+
structsubre*newlacons;
18271843
structsubre*sub;
18281844

18291845
if (v->nlacons==0)
18301846
{
1831-
v->lacons= (structsubre*)MALLOC(2*sizeof(structsubre));
18321847
n=1;/* skip 0th */
1833-
v->nlacons=2;
1848+
newlacons=(structsubre*)MALLOC(2*sizeof(structsubre));
18341849
}
18351850
else
18361851
{
1837-
v->lacons=(structsubre*)REALLOC(v->lacons,
1838-
(v->nlacons+1)*sizeof(structsubre));
1839-
n=v->nlacons++;
1852+
n=v->nlacons;
1853+
newlacons=(structsubre*)REALLOC(v->lacons,
1854+
(n+1)*sizeof(structsubre));
18401855
}
1841-
if (v->lacons==NULL)
1856+
if (newlacons==NULL)
18421857
{
18431858
ERR(REG_ESPACE);
18441859
return0;
18451860
}
1861+
v->lacons=newlacons;
1862+
v->nlacons=n+1;
18461863
sub=&v->lacons[n];
18471864
sub->begin=begin;
18481865
sub->end=end;

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