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Further tweak memory management for regex DFAs.

Mon, 8 Mar 2021 21:32:29 +0000 (16:32 -0500)

Coverity is still unhappy after commit 190c79884, and after looking
closer I think it might be onto something. The callers of newdfa()
typically drop out if v->err has been set nonzero, which newdfa()
is faithfully doing if it fails. However, what if v->err was already
nonzero before we entered newdfa()? Then newdfa() could succeed and
the caller would promptly leak its result.

I don't think this scenario can actually happen, but the predicate
"v->err is always zero when newdfa() is called" seems difficult to be
entirely sure of; there's a good deal of code that potentially could
get that wrong.

It seems better to adjust the callers to directly check for a null
result instead of relying on ISERR() tests. This is slightly cheaper
than the previous coding anyway.

Lacking evidence that there's any real bug, no back-patch.

src/backend/regex/rege_dfa.c patch | blob | blame | history

src/backend/regex/regexec.c patch | blob | blame | history

diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c

index 18f87c69d4754f6a4e17a55b4e7b65875633154d..1d79d734468f94db502ad3db599cfbc5553134cf 100644 (file)

--- a/src/backend/regex/rege_dfa.c

+++ b/src/backend/regex/rege_dfa.c

@@ -604,6 +604,8 @@ lastcold(struct vars *v,

* newdfa - set up a fresh DFA

+ *

+ * Returns NULL (and sets v->err) on failure.

static struct dfa *

newdfa(struct vars *v,

diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c

index 8d7777f8c62ff4eb0a8a8502a998e155df83b8a4..5b9a0878203224effce404e8e798cfaa37348cc4 100644 (file)

--- a/src/backend/regex/regexec.c

+++ b/src/backend/regex/regexec.c

@@ -351,7 +351,7 @@ getsubdfa(struct vars *v,

if (d == NULL)

{

d = newdfa(v, &t->cnfa, &v->g->cmap, DOMALLOC);

- if (ISERR())

+ if (d == NULL)

return NULL;

/* set up additional info if this is a backref node */

if (t->op == 'b')

@@ -381,8 +381,6 @@ getladfa(struct vars *v,

struct subre *sub = &v->g->lacons[n];

v->ladfas[n] = newdfa(v, &sub->cnfa, &v->g->cmap, DOMALLOC);

- if (ISERR())

- return NULL;

/* a LACON can't contain a backref, so nothing else to do */

}

return v->ladfas[n];

@@ -408,8 +406,8 @@ find(struct vars *v,

/* first, a shot with the search RE */

s = newdfa(v, &v->g->search, cm, &v->dfa1);

- assert(!(ISERR() && s != NULL));

- NOERR();

+ if (s == NULL)

+ return v->err;

MDEBUG(("\nsearch at %ld\n", LOFF(v->start)));

cold = NULL;

close = shortest(v, s, v->search_start, v->search_start, v->stop,

@@ -436,8 +434,8 @@ find(struct vars *v,

cold = NULL;

MDEBUG(("between %ld and %ld\n", LOFF(open), LOFF(close)));

d = newdfa(v, cnfa, cm, &v->dfa1);

- assert(!(ISERR() && d != NULL));

- NOERR();

+ if (d == NULL)

+ return v->err;

for (begin = open; begin <= close; begin++)

{

MDEBUG(("\nfind trying at %ld\n", LOFF(begin)));

@@ -493,11 +491,11 @@ cfind(struct vars *v,

int ret;

s = newdfa(v, &v->g->search, cm, &v->dfa1);

- NOERR();

+ if (s == NULL)

+ return v->err;

d = newdfa(v, cnfa, cm, &v->dfa2);

- if (ISERR())

+ if (d == NULL)

{

- assert(d == NULL);

freedfa(s);

return v->err;

}

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