m2sm() converts a u32 slope to a u64 scaled value. For large inputs (e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores the difference of two such u64 values in a u32 variable `dsm` and uses it as a divisor. When the difference is exactly 2^32 the truncation yields zero, causing a divide-by-zero oops in the concave-curve intersection path: Oops: divide error: 0000 RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601) Call Trace: init_ed (net/sched/sch_hfsc.c:629) hfsc_enqueue (net/sched/sch_hfsc.c:1569) [...] Widen `dsm` to u64 and replace do_div() with div64_u64() so the full difference is preserved. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Weiming Shi Signed-off-by: Xiang Mei --- v2: resend to netdev ML v3: append selftest in 2/2 net/sched/sch_hfsc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index b5657ffbbf84..83b2ca2e37fc 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -555,7 +555,7 @@ static void rtsc_min(struct runtime_sc *rtsc, struct internal_sc *isc, u64 x, u64 y) { u64 y1, y2, dx, dy; - u32 dsm; + u64 dsm; if (isc->sm1 <= isc->sm2) { /* service curve is convex */ @@ -598,7 +598,7 @@ rtsc_min(struct runtime_sc *rtsc, struct internal_sc *isc, u64 x, u64 y) */ dx = (y1 - y) << SM_SHIFT; dsm = isc->sm1 - isc->sm2; - do_div(dx, dsm); + dx = div64_u64(dx, dsm); /* * check if (x, y1) belongs to the 1st segment of rtsc. * if so, add the offset. -- 2.43.0 Add a regression test for the divide-by-zero in rtsc_min() triggered when m2sm() converts a large m1 value (e.g. 32gbit) to a u64 scaled slope reaching 2^32. rtsc_min() stores the difference of two such u64 values (sm1 - sm2) in a u32 variable `dsm`, truncating 2^32 to zero and causing a divide-by-zero oops in the concave-curve intersection path. The test configures an HFSC class with m1=32gbit d=1ms m2=0bit, sends a packet to activate the class, waits for it to drain and go idle, then sends another packet to trigger reactivation through rtsc_min(). Signed-off-by: Xiang Mei --- v3: append selftest in 2/2 .../tc-testing/tc-tests/infra/qdiscs.json | 25 +++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json index 6a39640aa2a8..1e5efb2a31eb 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json +++ b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json @@ -1111,5 +1111,30 @@ "teardown": [ "$TC qdisc del dev $DUMMY root handle 1:" ] + }, + { + "id": "a3d7", + "name": "HFSC with large m1 - no divide-by-zero on class reactivation", + "category": [ + "qdisc", + "hfsc" + ], + "plugins": { + "requires": "nsPlugin" + }, + "setup": [ + "$TC qdisc replace dev $DUMMY root handle 1: hfsc default 1", + "$TC class replace dev $DUMMY parent 1: classid 1:1 hfsc rt m1 32gbit d 1ms m2 0bit ls m1 32gbit d 1ms m2 0bit", + "ping -I$DUMMY -f -c1 -s64 -W1 10.10.10.1 || true", + "sleep 1" + ], + "cmdUnderTest": "ping -I$DUMMY -f -c1 -s64 -W1 10.10.10.1 || true", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DUMMY", + "matchPattern": "qdisc hfsc 1: root", + "matchCount": "1", + "teardown": [ + "$TC qdisc del dev $DUMMY handle 1: root" + ] } ] -- 2.43.0