The four nexthop torture subtests delete and re-add a group member
while ping -f and mausezahn keep traffic flowing through the same
group, so on each iteration the read side runs nh_grp_entry_stats_inc()
while the write side goes through remove_nh_grp_entry(). That is the
exact race fixed in commit b2662e7593e9 ("net: nexthop: fix percpu
use-after-free in remove_nh_grp_entry").The reason it never tripped these tests is the assertion. Each subtest ends with "if we did not crash, success", so a KASAN splat without panic_on_warn=1 lands in dmesg and the test still prints [OK]. The UAF above would have been visible to a KASAN run of fib_nexthops.sh; the torture loop just did not bother to look. Drop a marker into /dev/kmsg before each torture subtest, grep for KASAN/UBSAN/KCSAN/KFENCE/Oops/"kernel BUG at" lines once the load is killed, and fail the subtest with the offending lines printed if any match. The check is skipped when /dev/kmsg is not writable so the existing pass behaviour is preserved on restricted setups. No new TEST_PROGS, no new test mechanism, just close the assertion gap. Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Vastargazing <[email protected]> --- tools/testing/selftests/net/fib_nexthops.sh | 69 ++++++++++++++++++--- 1 file changed, 61 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/net/fib_nexthops.sh b/tools/testing/selftests/net/fib_nexthops.sh index ac868a731694..41c8767fc310 100755 --- a/tools/testing/selftests/net/fib_nexthops.sh +++ b/tools/testing/selftests/net/fib_nexthops.sh @@ -128,6 +128,47 @@ run_cmd() return $rc } +# Helpers used by the *_torture subtests below. The torture loops drive +# concurrent nexthop updates and packet flood, but until now they only +# checked "did the kernel crash". A KASAN/UBSAN report without +# panic_on_warn=1 lands in dmesg and is silently ignored. These helpers +# place a marker into /dev/kmsg before the load starts and grep for +# splat lines after it stops. If /dev/kmsg is not writable the check +# is skipped and the previous pass behaviour is kept. +torture_dmesg_marker="" + +torture_dmesg_baseline() +{ + torture_dmesg_marker="" + [ -w /dev/kmsg ] || return 0 + + torture_dmesg_marker="fib_nexthops-torture-$$-$RANDOM" + echo "$torture_dmesg_marker" >/dev/kmsg +} + +torture_dmesg_check() +{ + local since + local found + + [ -z "$torture_dmesg_marker" ] && return 0 + + since=$(dmesg 2>/dev/null | \ + awk -v m="$torture_dmesg_marker" ' + $0 ~ m { f = 1; next } + f { print } + ') + + found=$(echo "$since" | grep -E \ + 'KASAN:|UBSAN:|KCSAN:|KFENCE:|Oops:|kernel BUG at|general protection fault') + + [ -z "$found" ] && return 0 + + echo " Kernel splat detected during torture run:" + echo "$found" | sed 's/^/ /' + return 1 +} + get_linklocal() { local dev=$1 @@ -1333,6 +1374,8 @@ ipv6_torture() run_cmd "$IP route add 2001:db8:101::1 nhid 102" run_cmd "$IP route add 2001:db8:101::2 nhid 102" + torture_dmesg_baseline + ipv6_del_add_loop1 & pid1=$! ipv6_grp_replace_loop & @@ -1348,8 +1391,9 @@ ipv6_torture() kill -9 $pid1 $pid2 $pid3 $pid4 $pid5 wait $pid1 $pid2 $pid3 $pid4 $pid5 2>/dev/null - # if we did not crash, success - log_test 0 0 "IPv6 torture test" + # Pass only if we did not crash AND no kernel splat appeared. + torture_dmesg_check + log_test $? 0 "IPv6 torture test" } ipv6_res_grp_replace_loop() @@ -1387,6 +1431,8 @@ ipv6_res_torture() run_cmd "$IP route add 2001:db8:101::1 nhid 102" run_cmd "$IP route add 2001:db8:101::2 nhid 102" + torture_dmesg_baseline + ipv6_del_add_loop1 & pid1=$! ipv6_res_grp_replace_loop & @@ -1404,8 +1450,9 @@ ipv6_res_torture() kill -9 $pid1 $pid2 $pid3 $pid4 $pid5 wait $pid1 $pid2 $pid3 $pid4 $pid5 2>/dev/null - # if we did not crash, success - log_test 0 0 "IPv6 resilient nexthop group torture test" + # Pass only if we did not crash AND no kernel splat appeared. + torture_dmesg_check + log_test $? 0 "IPv6 resilient nexthop group torture test" } ipv4_fcnal() @@ -2123,6 +2170,8 @@ ipv4_torture() run_cmd "$IP route add 172.16.101.1 nhid 102" run_cmd "$IP route add 172.16.101.2 nhid 102" + torture_dmesg_baseline + ipv4_del_add_loop1 & pid1=$! ipv4_grp_replace_loop & @@ -2138,8 +2187,9 @@ ipv4_torture() kill -9 $pid1 $pid2 $pid3 $pid4 $pid5 wait $pid1 $pid2 $pid3 $pid4 $pid5 2>/dev/null - # if we did not crash, success - log_test 0 0 "IPv4 torture test" + # Pass only if we did not crash AND no kernel splat appeared. + torture_dmesg_check + log_test $? 0 "IPv4 torture test" } ipv4_res_grp_replace_loop() @@ -2177,6 +2227,8 @@ ipv4_res_torture() run_cmd "$IP route add 172.16.101.1 nhid 102" run_cmd "$IP route add 172.16.101.2 nhid 102" + torture_dmesg_baseline + ipv4_del_add_loop1 & pid1=$! ipv4_res_grp_replace_loop & @@ -2194,8 +2246,9 @@ ipv4_res_torture() kill -9 $pid1 $pid2 $pid3 $pid4 $pid5 wait $pid1 $pid2 $pid3 $pid4 $pid5 2>/dev/null - # if we did not crash, success - log_test 0 0 "IPv4 resilient nexthop group torture test" + # Pass only if we did not crash AND no kernel splat appeared. + torture_dmesg_check + log_test $? 0 "IPv4 resilient nexthop group torture test" } basic() -- 2.51.0
