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Data flow: Track access path lengths in stages 3 and 4 #22392

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68 changes: 48 additions & 20 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class ApNil extends Ap;

predicate apTracksLength();

bindingset[result, ap]
ApApprox getApprox(Ap ap);

Expand Down Expand Up @@ -563,6 +565,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

pragma[nomagic]
private int getAnApLengthLowerBound(Ap ap) {
not apTracksLength() and // no need if we are tracking precise length information
accessPathLimit() > 1 and // `accessPathLimit() <= 1` is already checked in stages 1 and 2
ap instanceof ApNil and
result = 0
Expand Down Expand Up @@ -609,7 +612,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
fwdFlowStore(_, _, ap0, _, c, t, stored, node, cc, summaryCtx) and
ap = apCons(c, ap0) and
apa = getApprox(ap) and
if accessPathLimit() > 1
if accessPathLimit() > 1 and not apTracksLength()
then getAnApLengthLowerBound(ap0) < accessPathLimit()
else any()
)
Expand Down Expand Up @@ -1339,6 +1342,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

pragma[nomagic]
private int getAnApLengthLowerBoundRev(Ap ap) {
not apTracksLength() and // no need if we are tracking precise length information
accessPathLimit() > 1 and // `accessPathLimit() <= 1` is already checked in stages 1 and 2
ap instanceof ApNil and
result = 0
Expand Down Expand Up @@ -1388,7 +1392,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
exists(Nd mid, Ap ap0 |
revFlow(mid, returnCtx, returnAp, ap0) and
readStepFwd(node, ap, _, mid, ap0) and
if accessPathLimit() > 1
if accessPathLimit() > 1 and not apTracksLength()
then getAnApLengthLowerBoundRev(ap0) < accessPathLimit()
else any()
)
Expand Down Expand Up @@ -2776,6 +2780,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
ApNil() { this = false }
}

predicate apTracksLength() { none() }

bindingset[result, ap]
PrevStage::Ap getApprox(Ap ap) { any() }

Expand Down Expand Up @@ -2854,17 +2860,26 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class ApNil = ApproxAccessPathFrontNil;

predicate apTracksLength() { any() }

PrevStage::Ap getApprox(Ap ap) { result = ap.toBoolNonEmpty() }

Typ getTyp(Type t) { any() }

bindingset[c, tail]
Ap apCons(Content c, Ap tail) { result.getAHead() = c and exists(tail) }
Ap apCons(Content c, Ap tail) {
exists(int length | result.getAHead(length) = c |
length = 1 and
tail instanceof ApNil
or
tail = TApproxFrontHead(_, length - 1)
)
}

class ApHeadContent = ContentApprox;

pragma[noinline]
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead() }
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead(_) }

predicate projectToHeadContent = getContentApproxCached/1;

Expand Down Expand Up @@ -2910,7 +2925,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
PrevStage::revFlow(node) and
PrevStage::readStepCand(_, c, _) and
Stage1::expectsContentEx(node, c) and
c = ap.getAHead()
c = ap.getAHead(_)
)
}

Expand Down Expand Up @@ -2956,17 +2971,26 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class ApNil = AccessPathFrontNil;

predicate apTracksLength() { any() }

PrevStage::Ap getApprox(Ap ap) { result = ap.toApprox() }

Typ getTyp(Type t) { any() }

bindingset[c, tail]
Ap apCons(Content c, Ap tail) { result.getHead() = c and exists(tail) }
Ap apCons(Content c, Ap tail) {
exists(int length | result.getHead(length) = c |
length = 1 and
tail instanceof ApNil
or
tail = TFrontHead(_, length - 1)
)
}

class ApHeadContent = Content;

pragma[noinline]
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead() }
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead(_) }

ApHeadContent projectToHeadContent(Content c) { result = c }

Expand Down Expand Up @@ -3012,19 +3036,19 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
// When `node` is the target of a store, we interpret `clearsContent` as
// only pertaining to _earlier_ store steps. In this case, we need to postpone
// checking `clearsContent` to the step creation.
clearContent(node, ap.getHead(), false)
clearContent(node, ap.getHead(_), false)
}

pragma[nomagic]
private predicate clearExceptStore(Nd node, Ap ap) { clearContent(node, ap.getHead(), true) }
private predicate clearExceptStore(Nd node, Ap ap) { clearContent(node, ap.getHead(_), true) }

pragma[nomagic]
private predicate expectsContentCand(Nd node, Ap ap) {
exists(Content c |
PrevStage::revFlow(node) and
PrevStage::readStepCand(_, c, _) and
Stage1::expectsContentEx(node, c) and
c = ap.getHead()
c = ap.getHead(_)
)
}

Expand Down Expand Up @@ -3059,9 +3083,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tails = strictcount(AccessPathFront apf | Stage4::consCand(c, apf)) and
nodes =
strictcount(Nd n |
Stage4::revFlow(n, any(AccessPathFrontHead apf | apf.getHead() = c))
Stage4::revFlow(n, any(AccessPathFrontHead apf | apf.getHead(_) = c))
or
Stage4::nodeMayUseSummary(n, any(AccessPathFrontHead apf | apf.getHead() = c))
Stage4::nodeMayUseSummary(n, any(AccessPathFrontHead apf | apf.getHead(_) = c))
) and
accessPathApproxCostLimits(apLimit, tupleLimit) and
apLimit < tails and
Expand All @@ -3077,7 +3101,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
not expensiveLen2unfolding(c)
} or
TConsCons(Content c1, Content c2, int len) {
Stage4::consCand(c1, TFrontHead(c2)) and
Stage4::consCand(c1, TFrontHead(c2, _)) and
len in [2 .. Config::accessPathLimit()] and
not expensiveLen2unfolding(c1)
} or
Expand Down Expand Up @@ -3131,7 +3155,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = 1 }

override AccessPathFront getFront() { result = TFrontHead(c) }
override AccessPathFront getFront() { result = TFrontHead(c, 1) }

override predicate isCons(Content head, AccessPathApprox tail) { head = c and tail = TNil() }
}
Expand All @@ -3153,7 +3177,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = len }

override AccessPathFront getFront() { result = TFrontHead(c1) }
override AccessPathFront getFront() { result = TFrontHead(c1, len) }

override predicate isCons(Content head, AccessPathApprox tail) {
head = c1 and
Expand Down Expand Up @@ -3184,12 +3208,12 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = len }

override AccessPathFront getFront() { result = TFrontHead(c) }
override AccessPathFront getFront() { result = TFrontHead(c, len) }

override predicate isCons(Content head, AccessPathApprox tail) {
head = c and
(
exists(Content c2 | Stage4::consCand(c, TFrontHead(c2)) |
exists(Content c2 | Stage4::consCand(c, TFrontHead(c2, len - 1)) |
tail = TConsCons(c2, _, len - 1)
or
len = 2 and
Expand Down Expand Up @@ -3226,6 +3250,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class ApNil = AccessPathApproxNil;

predicate apTracksLength() { any() }

pragma[nomagic]
PrevStage::Ap getApprox(Ap ap) { result = ap.getFront() }

Expand Down Expand Up @@ -3416,6 +3442,8 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class ApNil = AccessPathNil;

predicate apTracksLength() { any() }

pragma[nomagic]
PrevStage::Ap getApprox(Ap ap) { result = ap.getApprox() }

Expand Down Expand Up @@ -3531,7 +3559,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override predicate isCons(Content head, AccessPath tail) { head = head_ and tail = tail_ }

override AccessPathFrontHead getFront() { result = TFrontHead(head_) }
override AccessPathFrontHead getFront() { result = TFrontHead(head_, this.length()) }

override AccessPathApproxCons getApprox() {
result = TConsNil(head_) and tail_ = TAccessPathNil()
Expand Down Expand Up @@ -3586,7 +3614,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tail.length() = len - 1
}

override AccessPathFrontHead getFront() { result = TFrontHead(head1) }
override AccessPathFrontHead getFront() { result = TFrontHead(head1, len) }

override AccessPathApproxCons getApprox() {
result = TConsCons(head1, head2, len) or
Expand Down Expand Up @@ -3618,7 +3646,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tail.length() = len - 1
}

override AccessPathFrontHead getFront() { result = TFrontHead(head_) }
override AccessPathFrontHead getFront() { result = TFrontHead(head_, len) }

override AccessPathApproxCons getApprox() { result = TCons1(head_, len) }

Expand Down
27 changes: 12 additions & 15 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImplCommon.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -1797,12 +1797,12 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
cached
newtype TAccessPathFront =
TFrontNil() or
TFrontHead(Content c)
TFrontHead(Content c, int length) { length in [1 .. accessPathLimit()] }

cached
newtype TApproxAccessPathFront =
TApproxFrontNil() or
TApproxFrontHead(ContentApprox c)
TApproxFrontHead(ContentApprox c, int length) { length in [1 .. accessPathLimit()] }

cached
newtype TAccessPathFrontOption =
Expand Down Expand Up @@ -2505,15 +2505,10 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract boolean toBoolNonEmpty();

ContentApprox getHead() { this = TApproxFrontHead(result) }
ContentApprox getHead(int length) { this = TApproxFrontHead(result, length) }

pragma[nomagic]
Content getAHead() {
exists(ContentApprox cont |
this = TApproxFrontHead(cont) and
cont = getContentApproxCached(result)
)
}
Content getAHead(int length) { this.getHead(length) = getContentApproxCached(result) }
}

class ApproxAccessPathFrontNil extends ApproxAccessPathFront, TApproxFrontNil {
Expand All @@ -2524,10 +2519,11 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

class ApproxAccessPathFrontHead extends ApproxAccessPathFront, TApproxFrontHead {
private ContentApprox c;
private int length;

ApproxAccessPathFrontHead() { this = TApproxFrontHead(c) }
ApproxAccessPathFrontHead() { this = TApproxFrontHead(c, length) }

override string toString() { result = c.toString() }
override string toString() { result = c + " (length: " + length + ")" }

override boolean toBoolNonEmpty() { result = true }
}
Expand All @@ -2549,7 +2545,7 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract ApproxAccessPathFront toApprox();

Content getHead() { this = TFrontHead(result) }
Content getHead(int length) { this = TFrontHead(result, length) }
}

class AccessPathFrontNil extends AccessPathFront, TFrontNil {
Expand All @@ -2560,12 +2556,13 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

class AccessPathFrontHead extends AccessPathFront, TFrontHead {
private Content c;
private int length;

AccessPathFrontHead() { this = TFrontHead(c) }
AccessPathFrontHead() { this = TFrontHead(c, length) }

override string toString() { result = c.toString() }
override string toString() { result = c + " (length: " + length + ")" }

override ApproxAccessPathFront toApprox() { result.getAHead() = c }
override ApproxAccessPathFront toApprox() { result.getAHead(length) = c }
}

/** An optional access path front. */
Expand Down
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