Fix a memory leak issue on netpoll and create a netconsole test that exposes the problem, when run with kmemleak enabled.
This is a merge of two patches I've sent individually and are merged on the same patchset[1][2].
Link: https://lore.kernel.org/all/20250904-netconsole_torture-v2-0-5775ed5dc366@de... [1] Link: https://lore.kernel.org/all/20250902165426.6d6cd172@kernel.org/ [2]
Signed-off-by: Breno Leitao leitao@debian.org --- Changes in v3: - this patchset is a merge of the fix and the selftest together as recommended by Jakub.
Changes in v2: - Reuse the netconsole creation from lib_netcons.sh. Thus, refactoring the create_dynamic_target() (Jakub) - Move the "wait" to after all the messages has been sent. - Link to v1: https://lore.kernel.org/r/20250902-netconsole_torture-v1-1-03c6066598e9@debi...
--- Breno Leitao (3): netpoll: fix incorrect refcount handling causing incorrect cleanup selftest: netcons: refactor target creation selftest: netcons: create a torture test
net/core/netpoll.c | 7 +- tools/testing/selftests/drivers/net/Makefile | 1 + .../selftests/drivers/net/lib/sh/lib_netcons.sh | 30 +++-- .../selftests/drivers/net/netcons_torture.sh | 127 +++++++++++++++++++++ 4 files changed, 152 insertions(+), 13 deletions(-) --- base-commit: d69eb204c255c35abd9e8cb621484e8074c75eaa change-id: 20250902-netconsole_torture-8fc23f0aca99
Best regards, -- Breno Leitao leitao@debian.org
commit efa95b01da18 ("netpoll: fix use after free") incorrectly ignored the refcount and prematurely set dev->npinfo to NULL during netpoll cleanup, leading to improper behavior and memory leaks.
Scenario causing lack of proper cleanup:
1) A netpoll is associated with a NIC (e.g., eth0) and netdev->npinfo is allocated, and refcnt = 1 - Keep in mind that npinfo is shared among all netpoll instances. In this case, there is just one.
2) Another netpoll is also associated with the same NIC and npinfo->refcnt += 1. - Now dev->npinfo->refcnt = 2; - There is just one npinfo associated to the netdev.
3) When the first netpolls goes to clean up: - The first cleanup succeeds and clears np->dev->npinfo, ignoring refcnt. - It basically calls `RCU_INIT_POINTER(np->dev->npinfo, NULL);` - Set dev->npinfo = NULL, without proper cleanup - No ->ndo_netpoll_cleanup() is either called
4) Now the second target tries to clean up - The second cleanup fails because np->dev->npinfo is already NULL. * In this case, ops->ndo_netpoll_cleanup() was never called, and the skb pool is not cleaned as well (for the second netpoll instance) - This leaks npinfo and skbpool skbs, which is clearly reported by kmemleak.
Revert commit efa95b01da18 ("netpoll: fix use after free") and adds clarifying comments emphasizing that npinfo cleanup should only happen once the refcount reaches zero, ensuring stable and correct netpoll behavior.
Cc: stable@vger.kernel.org Cc: jv@jvosburgh.net Fixes: efa95b01da18 ("netpoll: fix use after free") Signed-off-by: Breno Leitao leitao@debian.org --- net/core/netpoll.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 5f65b62346d4e..19676cd379640 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -815,6 +815,10 @@ static void __netpoll_cleanup(struct netpoll *np) if (!npinfo) return;
+ /* At this point, there is a single npinfo instance per netdevice, and + * its refcnt tracks how many netpoll structures are linked to it. We + * only perform npinfo cleanup when the refcnt decrements to zero. + */ if (refcount_dec_and_test(&npinfo->refcnt)) { const struct net_device_ops *ops;
@@ -824,8 +828,7 @@ static void __netpoll_cleanup(struct netpoll *np)
RCU_INIT_POINTER(np->dev->npinfo, NULL); call_rcu(&npinfo->rcu, rcu_cleanup_netpoll_info); - } else - RCU_INIT_POINTER(np->dev->npinfo, NULL); + }
skb_pool_flush(np); }
Extract the netconsole target creation from create_dynamic_target(), by moving it from create_dynamic_target() into a new helper function. This enables other tests to use the creation of netconsole targets with arbitrary parameters and no sleep.
The new helper will be utilized by forthcoming torture-type selftests that require dynamic target management.
Signed-off-by: Breno Leitao leitao@debian.org --- .../selftests/drivers/net/lib/sh/lib_netcons.sh | 30 ++++++++++++++-------- 1 file changed, 19 insertions(+), 11 deletions(-)
diff --git a/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh b/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh index b6071e80ebbb6..4fc102407e3a6 100644 --- a/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh +++ b/tools/testing/selftests/drivers/net/lib/sh/lib_netcons.sh @@ -113,31 +113,39 @@ function set_network() { configure_ip }
-function create_dynamic_target() { - local FORMAT=${1:-"extended"} +function _create_dynamic_target() { + local FORMAT="${1:?FORMAT parameter required}" + local NCPATH="${2:?NCPATH parameter required}"
DSTMAC=$(ip netns exec "${NAMESPACE}" \ ip link show "${DSTIF}" | awk '/ether/ {print $2}')
# Create a dynamic target - mkdir "${NETCONS_PATH}" + mkdir "${NCPATH}"
- echo "${DSTIP}" > "${NETCONS_PATH}"/remote_ip - echo "${SRCIP}" > "${NETCONS_PATH}"/local_ip - echo "${DSTMAC}" > "${NETCONS_PATH}"/remote_mac - echo "${SRCIF}" > "${NETCONS_PATH}"/dev_name + echo "${DSTIP}" > "${NCPATH}"/remote_ip + echo "${SRCIP}" > "${NCPATH}"/local_ip + echo "${DSTMAC}" > "${NCPATH}"/remote_mac + echo "${SRCIF}" > "${NCPATH}"/dev_name
if [ "${FORMAT}" == "basic" ] then # Basic target does not support release - echo 0 > "${NETCONS_PATH}"/release - echo 0 > "${NETCONS_PATH}"/extended + echo 0 > "${NCPATH}"/release + echo 0 > "${NCPATH}"/extended elif [ "${FORMAT}" == "extended" ] then - echo 1 > "${NETCONS_PATH}"/extended + echo 1 > "${NCPATH}"/extended fi
- echo 1 > "${NETCONS_PATH}"/enabled + echo 1 > "${NCPATH}"/enabled + +} + +function create_dynamic_target() { + local FORMAT=${1:-"extended"} + local NCPATH=${2:-"$NETCONS_PATH"} + _create_dynamic_target "${FORMAT}" "${NCPATH}"
# This will make sure that the kernel was able to # load the netconsole driver configuration. The console message
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#opti...
Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree. Subject: [PATCH net v3 2/3] selftest: netcons: refactor target creation Link: https://lore.kernel.org/stable/20250905-netconsole_torture-v3-2-875c7febd316...
Create a netconsole test that puts a lot of pressure on the netconsole list manipulation. Do it by creating dynamic targets and deleting targets while messages are being sent. Also put interface down while the messages are being sent, as creating parallel targets.
The code launches three background jobs on distinct schedules:
* Toggle netcons target every 30 iterations * create and delete random_target every 50 iterations * toggle iface every 70 iterations
This creates multiple concurrency sources that interact with netconsole states. This is good practice to simulate stress, and exercise netpoll and netconsole locks.
This test already found an issue as reported in [1]
Link: https://lore.kernel.org/all/20250901-netpoll_memleak-v1-1-34a181977dfc@debia... [1] Signed-off-by: Breno Leitao leitao@debian.org Reviewed-by: Andre Carvalho asantostc@gmail.com --- tools/testing/selftests/drivers/net/Makefile | 1 + .../selftests/drivers/net/netcons_torture.sh | 127 +++++++++++++++++++++ 2 files changed, 128 insertions(+)
diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile index 984ece05f7f92..2b253b1ff4f38 100644 --- a/tools/testing/selftests/drivers/net/Makefile +++ b/tools/testing/selftests/drivers/net/Makefile @@ -17,6 +17,7 @@ TEST_PROGS := \ netcons_fragmented_msg.sh \ netcons_overflow.sh \ netcons_sysdata.sh \ + netcons_torture.sh \ netpoll_basic.py \ ping.py \ queues.py \ diff --git a/tools/testing/selftests/drivers/net/netcons_torture.sh b/tools/testing/selftests/drivers/net/netcons_torture.sh new file mode 100755 index 0000000000000..3608051d475ff --- /dev/null +++ b/tools/testing/selftests/drivers/net/netcons_torture.sh @@ -0,0 +1,127 @@ +#!/usr/bin/env bash +# SPDX-License-Identifier: GPL-2.0 + +# Repeatedly send kernel messages, toggles netconsole targets on and off, +# creates and deletes targets in parallel, and toggles the source interface to +# simulate stress conditions. +# +# This test aims to verify the robustness of netconsole under dynamic +# configurations and concurrent operations. +# +# The major goal is to run this test with LOCKDEP, Kmemleak and KASAN to make +# sure no issues is reported. +# +# Author: Breno Leitao leitao@debian.org + +set -euo pipefail + +SCRIPTDIR=$(dirname "$(readlink -e "${BASH_SOURCE[0]}")") + +source "${SCRIPTDIR}"/lib/sh/lib_netcons.sh + +# Number of times the main loop run +ITERATIONS=${1:-1000} + +# Only test extended format +FORMAT="extended" +# And ipv6 only +IP_VERSION="ipv6" + +# Create, enable and delete some targets. +create_and_delete_random_target() { + COUNT=2 + RND_PREFIX=$(mktemp -u netcons_rnd_XXXX_) + + if [ -d "${NETCONS_CONFIGFS}/${RND_PREFIX}${COUNT}" ] || \ + [ -d "${NETCONS_CONFIGFS}/${RND_PREFIX}0" ]; then + echo "Function didn't finish yet, skipping it." >&2 + return + fi + + # enable COUNT targets + for i in $(seq ${COUNT}) + do + RND_TARGET="${RND_PREFIX}"${i} + RND_TARGET_PATH="${NETCONS_CONFIGFS}"/"${RND_TARGET}" + + # Basic population so the target can come up + _create_dynamic_target "${FORMAT}" "${RND_TARGET_PATH}" + done + + echo "netconsole selftest: ${COUNT} additional targets were created" > /dev/kmsg + # disable them all + for i in $(seq ${COUNT}) + do + RND_TARGET="${RND_PREFIX}"${i} + RND_TARGET_PATH="${NETCONS_CONFIGFS}"/"${RND_TARGET}" + echo 0 > "${RND_TARGET_PATH}"/enabled + rmdir "${RND_TARGET_PATH}" + done +} + +# Disable and enable the target mid-air, while messages +# are being transmitted. +toggle_netcons_target() { + for i in $(seq 2) + do + if [ ! -d "${NETCONS_PATH}" ] + then + break + fi + echo 0 > "${NETCONS_PATH}"/enabled 2> /dev/null || true + # Try to enable a bit harder, given it might fail to enable + # Write to `enabled` might fail depending on the lock, which is + # highly contentious here + for _ in $(seq 5) + do + echo 1 > "${NETCONS_PATH}"/enabled 2> /dev/null || true + done + done +} + +toggle_iface(){ + ip link set "${SRCIF}" down + ip link set "${SRCIF}" up +} + +# Start here + +modprobe netdevsim 2> /dev/null || true +modprobe netconsole 2> /dev/null || true + +# Check for basic system dependency and exit if not found +check_for_dependencies +# Set current loglevel to KERN_INFO(6), and default to KERN_NOTICE(5) +echo "6 5" > /proc/sys/kernel/printk +# Remove the namespace, interfaces and netconsole target on exit +trap cleanup EXIT +# Create one namespace and two interfaces +set_network "${IP_VERSION}" +# Create a dynamic target for netconsole +create_dynamic_target "${FORMAT}" + +for i in $(seq "$ITERATIONS") +do + for _ in $(seq 10) + do + echo "${MSG}: ${TARGET} ${i}" > /dev/kmsg + done + wait + + if (( i % 30 == 0 )); then + toggle_netcons_target & + fi + + if (( i % 50 == 0 )); then + # create some targets, enable them, send msg and disable + # all in a parallel thread + create_and_delete_random_target & + fi + + if (( i % 70 == 0 )); then + toggle_iface & + fi +done +wait + +exit "${ksft_pass}"
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Breno Leitao -
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