Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
hvitved wants to merge 2 commits into
base: main
Choose a base branch
from
+79 −55
Open

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

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
0d8e951
Data flow: Track access path lengths in stages 3 and 4
hvitved Aug 19, 2026
dfe567a
Potential fix for pull request finding
hvitved Aug 21, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
95 changes: 55 additions & 40 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -370,6 +370,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
}

class Ap {
/** Gets the tracked length of this access path, if any. */
int length();

string toString();
}

Expand Down Expand Up @@ -563,10 +566,10 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

pragma[nomagic]
private int getAnApLengthLowerBound(Ap ap) {
accessPathLimit() > 1 and // `accessPathLimit() <= 1` is already checked in stages 1 and 2
ap instanceof ApNil and
result = 0
accessPathLimit() != 0 and // `accessPathLimit() = 0` is already checked in `useFieldFlow`
result = ap.length()
or
not exists(ap.length()) and
exists(Ap tail |
fwdFlowConsCand(_, ap, _, _, tail) and
ap != tail and // no need to report a longer length
Expand Down Expand Up @@ -609,9 +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
then getAnApLengthLowerBound(ap0) < accessPathLimit()
else any()
getAnApLengthLowerBound(ap0) < accessPathLimit()
)
or
// read
Expand Down Expand Up @@ -1339,10 +1340,10 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

pragma[nomagic]
private int getAnApLengthLowerBoundRev(Ap ap) {
accessPathLimit() > 1 and // `accessPathLimit() <= 1` is already checked in stages 1 and 2
ap instanceof ApNil and
result = 0
accessPathLimit() != 0 and // `accessPathLimit() = 0` is already checked in `useFieldFlow`
result = ap.length()
or
not exists(ap.length()) and
exists(Ap tail |
revFlowConsCand(ap, _, tail) and
ap != tail and // no need to report a longer length
Expand Down Expand Up @@ -1388,9 +1389,7 @@ 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
then getAnApLengthLowerBoundRev(ap0) < accessPathLimit()
else any()
getAnApLengthLowerBoundRev(ap0) < accessPathLimit()
)
or
// flow into a callable
Expand Down Expand Up @@ -2770,7 +2769,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

class Typ = Unit;

class Ap = Boolean;
class Ap extends Boolean {
int length() { this = false and result = 0 }
}

class ApNil extends Ap {
ApNil() { this = false }
Expand Down Expand Up @@ -2859,12 +2860,19 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
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 +2918,7 @@ 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 @@ -2961,12 +2969,19 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
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 +3027,19 @@ 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 +3074,9 @@ 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 +3092,7 @@ 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
Comment thread
hvitved marked this conversation as resolved.
Outdated
len in [2 .. Config::accessPathLimit()] and
not expensiveLen2unfolding(c1)
} or
Expand All @@ -3098,7 +3113,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

abstract Content getHead();

abstract int len();
abstract int length();

abstract AccessPathFront getFront();

Expand All @@ -3111,7 +3126,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override Content getHead() { none() }

override int len() { result = 0 }
override int length() { result = 0 }

override AccessPathFront getFront() { result = TFrontNil() }

Expand All @@ -3129,9 +3144,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override Content getHead() { result = c }

override int len() { result = 1 }
override int length() { 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 @@ -3151,9 +3166,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override Content getHead() { result = c1 }

override int len() { result = len }
override int length() { 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 @@ -3182,14 +3197,14 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override Content getHead() { result = c }

override int len() { result = len }
override int length() { 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 @@ -3288,7 +3303,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

pragma[nomagic]
private predicate stage5ConsCand(Content c, AccessPathFront apf, int len) {
Stage5::consCand(c, any(AccessPathApprox ap | ap.getFront() = apf and ap.len() = len - 1))
Stage5::consCand(c, any(AccessPathApprox ap | ap.getFront() = apf and ap.length() = len - 1))
}

/**
Expand All @@ -3297,7 +3312,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
private int count1to2unfold(AccessPathApproxCons1 apa) {
exists(Content c, int len |
c = apa.getHead() and
len = apa.len() and
len = apa.length() and
result = strictcount(AccessPathFront apf | stage5ConsCand(c, apf, len))
)
}
Expand Down Expand Up @@ -3392,7 +3407,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
exists(AccessPathApproxCons apa, AccessPathApprox tail |
evalUnfold(apa, false) and
not expensiveLen1to2unfolding(apa) and
apa.len() = len and
apa.length() = len and
hasTail(apa, tail) and
head1 = apa.getHead() and
head2 = tail.getHead()
Expand All @@ -3402,7 +3417,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
exists(AccessPathApproxCons apa |
evalUnfold(apa, false) and
expensiveLen1to2unfolding(apa) and
apa.len() = len and
apa.length() = len and
head = apa.getHead()
)
}
Expand Down Expand Up @@ -3531,7 +3546,7 @@ 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 +3601,7 @@ 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 +3633,7 @@ 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
39 changes: 24 additions & 15 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImplCommon.qll
View file
Open in desktop
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 @@ -2505,31 +2505,33 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract boolean toBoolNonEmpty();

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

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 {
override string toString() { result = "nil" }

override boolean toBoolNonEmpty() { result = false }

override int length() { result = 0 }
}

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 }

override int length() { result = length }
}

/** An optional approximated access path front. */
Expand All @@ -2549,23 +2551,30 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract ApproxAccessPathFront toApprox();

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

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

class AccessPathFrontNil extends AccessPathFront, TFrontNil {
override string toString() { result = "nil" }

override ApproxAccessPathFront toApprox() { result = TApproxFrontNil() }

override int length() { result = 0 }
}

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

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

AccessPathFrontHead() { this = TFrontHead(c) }
override string toString() { result = c + " (length: " + length + ")" }

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

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

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