From patchwork Mon Sep 27 16:37:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Chamberlain X-Patchwork-Id: 12520403 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 937FDC4167E for ; Mon, 27 Sep 2021 16:38:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 802B3610E8 for ; Mon, 27 Sep 2021 16:38:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235758AbhI0Qk2 (ORCPT ); Mon, 27 Sep 2021 12:40:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235466AbhI0Qjv (ORCPT ); Mon, 27 Sep 2021 12:39:51 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35B04C061604; Mon, 27 Sep 2021 09:38:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=EpDjr2uCtpoo1VfT10KJe6h28mfil8D37PYMRkMG410=; b=x8pVhPuVe4/o1DO0FrsSX0aCK8 2Jm5eAMk2S8zLqo0VmRspazYqod+6OWWbxoMwQY33NFrnbib4CTRlK/vF3SGQ2NqUsD/FYstT3Mxy xsWI7vG9qNy3NQVt3ut/bmQo5rluaJWmsHmEjUZ44mrVuZAE3L7aq1l2+TuvK9+tQBHv+NWLnIgiq xly60QgQYRYZx5RJVgF8eA0eXxMfNXT1CKg0wYSySRHaZCK1B10XxcGawGLxUqmgcL1ND9SjXyIvY e57Wyg2tXBvwKmqvUGUEus+HjcRz5rtx0pPD+Sq1TCT8UEkqWyWWIQE84Wpd7g4xdVE3hXWRinKbj WGr351wg==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mUtdm-003OS7-Ot; Mon, 27 Sep 2021 16:38:06 +0000 From: Luis Chamberlain To: tj@kernel.org, gregkh@linuxfoundation.org, akpm@linux-foundation.org, minchan@kernel.org, jeyu@kernel.org, shuah@kernel.org Cc: bvanassche@acm.org, dan.j.williams@intel.com, joe@perches.com, tglx@linutronix.de, mcgrof@kernel.org, keescook@chromium.org, rostedt@goodmis.org, linux-spdx@vger.kernel.org, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 05/12] test_sysfs: add support to use kernfs failure injection Date: Mon, 27 Sep 2021 09:37:58 -0700 Message-Id: <20210927163805.808907-6-mcgrof@kernel.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210927163805.808907-1-mcgrof@kernel.org> References: <20210927163805.808907-1-mcgrof@kernel.org> MIME-Version: 1.0 Sender: Luis Chamberlain Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This extends test_sysfs with support for using the failure injection wait completion and knobs to force a few race conditions which demonstrates that kernfs active reference protection is sufficient for kobject / device protection at higher layers. This adds 4 new tests which tries to remove the device attribute store operation in 4 different situations: 1) at the start of kernfs_kernfs_fop_write_iter() 2) before the of->mutex is held in kernfs_kernfs_fop_write_iter() 3) after the of->mutex is held in kernfs_kernfs_fop_write_iter() 4) after the kernfs node active reference is taken A write fails in call cases except the last one, test number #32. There is a good explanation for this: *once* kernfs_get_active() gets called we have a guarantee that the kernfs entry cannot be removed. If kernfs_get_active() succeeds that entry cannot be removed and so anything trying to remove that entry will have to wait. It is perhaps not obvious but since a sysfs write will trigger eventually a kernfs_get_active() call, and *only* if this succeeds will the sysfs op be called, this and the fact that you cannot remove the kernfs entry while the kenfs entry is active implies that a module that created the respective sysfs / kernfs entry *cannot* possibly be removed during a sysfs operation. And test number 32 provides us with proof of this. If it were not true test #32 should crash. No null dereferences are reproduced, even though this has been observed in some complex testing cases [0]. If this issue really exists we should have enough tools on the sysfs_test toolbox now to try to reproduce this easily without having to poke around other drivers. It very likley was the case that the issue reported [0] was possibly a side issue after the first bug which was zram specific. This is why it is important to isolate the issue and try to reproduce it in a generic form using the test_sysfs driver. [0] https://lkml.kernel.org/r/20210623215007.862787-1-mcgrof@kernel.org Signed-off-by: Luis Chamberlain --- lib/Kconfig.debug | 3 + lib/test_sysfs.c | 31 +++++ tools/testing/selftests/sysfs/config | 3 + tools/testing/selftests/sysfs/sysfs.sh | 175 +++++++++++++++++++++++++ 4 files changed, 212 insertions(+) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a29b7d398c4e..176b822654e5 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2358,6 +2358,9 @@ config TEST_SYSFS depends on SYSFS depends on NET depends on BLOCK + select FAULT_INJECTION + select FAULT_INJECTION_DEBUG_FS + select FAIL_KERNFS_KNOBS help This builds the "test_sysfs" module. This driver enables to test the sysfs file system safely without affecting production knobs which diff --git a/lib/test_sysfs.c b/lib/test_sysfs.c index 2043ca494af8..c6e62de61403 100644 --- a/lib/test_sysfs.c +++ b/lib/test_sysfs.c @@ -38,6 +38,11 @@ #include #include #include +#include + +#ifdef CONFIG_FAIL_KERNFS_KNOBS +MODULE_IMPORT_NS(KERNFS_DEBUG_PRIVATE); +#endif static bool enable_lock; module_param(enable_lock, bool_enable_only, 0644); @@ -82,6 +87,13 @@ static bool enable_verbose_rmmod; module_param(enable_verbose_rmmod, bool_enable_only, 0644); MODULE_PARM_DESC(enable_verbose_rmmod, "enable verbose print messages on rmmod"); +#ifdef CONFIG_FAIL_KERNFS_KNOBS +static bool enable_completion_on_rmmod; +module_param(enable_completion_on_rmmod, bool_enable_only, 0644); +MODULE_PARM_DESC(enable_completion_on_rmmod, + "enable sending a kernfs completion on rmmod"); +#endif + static int sysfs_test_major; /** @@ -285,6 +297,12 @@ static ssize_t config_show(struct device *dev, "enable_verbose_writes:\t%s\n", enable_verbose_writes ? "true" : "false"); +#ifdef CONFIG_FAIL_KERNFS_KNOBS + len += snprintf(buf+len, PAGE_SIZE - len, + "enable_completion_on_rmmod:\t%s\n", + enable_completion_on_rmmod ? "true" : "false"); +#endif + test_dev_config_unlock(test_dev); return len; @@ -904,10 +922,23 @@ static int __init test_sysfs_init(void) } module_init(test_sysfs_init); +#ifdef CONFIG_FAIL_KERNFS_KNOBS +/* The goal is to race our device removal with a pending kernfs -> store call */ +static void test_sysfs_kernfs_send_completion_rmmod(void) +{ + if (!enable_completion_on_rmmod) + return; + complete(&kernfs_debug_wait_completion); +} +#else +static inline void test_sysfs_kernfs_send_completion_rmmod(void) {} +#endif + static void __exit test_sysfs_exit(void) { if (enable_debugfs) debugfs_remove(debugfs_dir); + test_sysfs_kernfs_send_completion_rmmod(); if (delay_rmmod_ms) msleep(delay_rmmod_ms); unregister_test_dev_sysfs(first_test_dev); diff --git a/tools/testing/selftests/sysfs/config b/tools/testing/selftests/sysfs/config index 9196f452ecd5..2876a229f95b 100644 --- a/tools/testing/selftests/sysfs/config +++ b/tools/testing/selftests/sysfs/config @@ -1,2 +1,5 @@ CONFIG_SYSFS=m CONFIG_TEST_SYSFS=m +CONFIG_FAULT_INJECTION=y +CONFIG_FAULT_INJECTION_DEBUG_FS=y +CONFIG_FAIL_KERNFS_KNOBS=y diff --git a/tools/testing/selftests/sysfs/sysfs.sh b/tools/testing/selftests/sysfs/sysfs.sh index b3f4c2236c7f..f928635d0e35 100755 --- a/tools/testing/selftests/sysfs/sysfs.sh +++ b/tools/testing/selftests/sysfs/sysfs.sh @@ -62,6 +62,10 @@ ALL_TESTS="$ALL_TESTS 0025:1:1:test_dev_y:block" ALL_TESTS="$ALL_TESTS 0026:1:1:test_dev_y:block" ALL_TESTS="$ALL_TESTS 0027:1:0:test_dev_x:block" # deadlock test ALL_TESTS="$ALL_TESTS 0028:1:0:test_dev_x:block" # deadlock test with rntl_lock +ALL_TESTS="$ALL_TESTS 0029:1:1:test_dev_x:block" # kernfs race removal of store +ALL_TESTS="$ALL_TESTS 0030:1:1:test_dev_x:block" # kernfs race removal before mutex +ALL_TESTS="$ALL_TESTS 0031:1:1:test_dev_x:block" # kernfs race removal after mutex +ALL_TESTS="$ALL_TESTS 0032:1:1:test_dev_x:block" # kernfs race removal after active allow_user_defaults() { @@ -92,6 +96,9 @@ allow_user_defaults() if [ -z $SYSFS_DEBUGFS_DIR ]; then SYSFS_DEBUGFS_DIR="/sys/kernel/debug/test_sysfs" fi + if [ -z $KERNFS_DEBUGFS_DIR ]; then + KERNFS_DEBUGFS_DIR="/sys/kernel/debug/kernfs" + fi if [ -z $PAGE_SIZE ]; then PAGE_SIZE=$(getconf PAGESIZE) fi @@ -167,6 +174,14 @@ modprobe_reset_enable_rtnl_lock_on_rmmod() unset FIRST_MODPROBE_ARGS } +modprobe_reset_enable_completion() +{ + FIRST_MODPROBE_ARGS="enable_completion_on_rmmod=1 enable_verbose_writes=1" + FIRST_MODPROBE_ARGS="$FIRST_MODPROBE_ARGS enable_verbose_rmmod=1 delay_rmmod_ms=0" + modprobe_reset + unset FIRST_MODPROBE_ARGS +} + load_req_mod() { modprobe_reset @@ -197,6 +212,63 @@ debugfs_reset_first_test_dev_ignore_errors() echo -n "1" >"$SYSFS_DEBUGFS_DIR"/reset_first_test_dev } +debugfs_kernfs_kernfs_fop_write_iter_exists() +{ + KNOB_DIR="${KERNFS_DEBUGFS_DIR}/config_fail_kernfs_fop_write_iter" + if [[ ! -d $KNOB_DIR ]]; then + echo "kernfs debugfs does not exist $KNOB_DIR" + return 0; + fi + KNOB_DEBUGFS="${KERNFS_DEBUGFS_DIR}/fail_kernfs_fop_write_iter" + if [[ ! -d $KNOB_DEBUGFS ]]; then + echo -n "kernfs debugfs for coniguring fail_kernfs_fop_write_iter " + echo "does not exist $KNOB_DIR" + return 0; + fi + return 1 +} + +debugfs_kernfs_kernfs_fop_write_iter_set_fail_once() +{ + KNOB_DEBUGFS="${KERNFS_DEBUGFS_DIR}/fail_kernfs_fop_write_iter" + echo 1 > $KNOB_DEBUGFS/interval + echo 100 > $KNOB_DEBUGFS/probability + echo 0 > $KNOB_DEBUGFS/space + # Disable verbose messages on the kernel ring buffer which may + # confuse developers with a kernel panic. + echo 0 > $KNOB_DEBUGFS/verbose + + # Fail only once + echo 1 > $KNOB_DEBUGFS/times +} + +debugfs_kernfs_kernfs_fop_write_iter_set_fail_never() +{ + KNOB_DEBUGFS="${KERNFS_DEBUGFS_DIR}/fail_kernfs_fop_write_iter" + echo 0 > $KNOB_DEBUGFS/times +} + +debugfs_kernfs_set_wait_ms() +{ + SLEEP_AFTER_WAIT_MS="${KERNFS_DEBUGFS_DIR}/sleep_after_wait_ms" + echo $1 > $SLEEP_AFTER_WAIT_MS +} + +debugfs_kernfs_disable_wait_kernfs_fop_write_iter() +{ + ENABLE_WAIT_KNOB="${KERNFS_DEBUGFS_DIR}/config_fail_kernfs_fop_write_iter/wait_" + for KNOB in ${ENABLE_WAIT_KNOB}*; do + echo 0 > $KNOB + done +} + +debugfs_kernfs_enable_wait_kernfs_fop_write_iter() +{ + ENABLE_WAIT_KNOB="${KERNFS_DEBUGFS_DIR}/config_fail_kernfs_fop_write_iter/wait_$1" + echo -n "1" > $ENABLE_WAIT_KNOB + return $? +} + set_orig() { if [[ ! -z $TARGET ]] && [[ ! -z $ORIG ]]; then @@ -972,6 +1044,105 @@ sysfs_test_0028() fi } +sysfs_race_kernfs_kernfs_fop_write_iter() +{ + TARGET="${DIR}/$(get_test_target $1)" + WAIT_AT=$2 + EXPECT_WRITE_RETURNS=$3 + MSDELAY=$4 + + modprobe_reset_enable_completion + ORIG=$(cat "${TARGET}") + TEST_STR=$(( $ORIG + 1 )) + + echo -n "Test racing removal of sysfs store op with kernfs $WAIT_AT ... " + + if debugfs_kernfs_kernfs_fop_write_iter_exists; then + echo -n "skipping test as CONFIG_FAIL_KERNFS_KNOBS " + echo " or CONFIG_FAULT_INJECTION_DEBUG_FS is disabled" + return $ksft_skip + fi + + # Allow for failing the kernfs_kernfs_fop_write_iter call once, + # we'll provide exact context shortly afterwards. + debugfs_kernfs_kernfs_fop_write_iter_set_fail_once + + # First disable all waits + debugfs_kernfs_disable_wait_kernfs_fop_write_iter + + # Enable a wait_for_completion(&kernfs_debug_wait_completion) at the + # specified location inside the kernfs_fop_write_iter() routine + debugfs_kernfs_enable_wait_kernfs_fop_write_iter $WAIT_AT + + # Configure kernfs so that after its wait_for_completion() it + # will msleep() this amount of time and schedule(). We figure this + # will be sufficient time to allow for our module removal to complete. + debugfs_kernfs_set_wait_ms $MSDELAY + + # Now we trigger a kernfs write op, which will run kernfs_fop_write_iter, + # but will wait until our driver sends a respective completion + set_test_ignore_errors & + write_pid=$! + + # At this point kernfs_fop_write_iter() hasn't run our op, its + # waiting for our completion at the specified time $WAIT_AT. + # We now remove our module which will send a + # complete(&kernfs_debug_wait_completion) right before we deregister + # our device and the sysfs device attributes are removed. + # + # After the completion is sent, the test_sysfs driver races with + # kernfs to do the device deregistration with the kernfs msleep + # and schedule(). This should mean we've forced trying to remove the + # module prior to allowing kernfs to run our store operation. If the + # race did happen we'll panic with a null dereference on the store op. + # + # If no race happens we should see no write operation triggered. + modprobe -r $TEST_DRIVER > /dev/null 2>&1 + + debugfs_kernfs_kernfs_fop_write_iter_set_fail_never + + wait $write_pid + if [[ $? -eq $EXPECT_WRITE_RETURNS ]]; then + echo "ok" + else + echo "FAIL" >&2 + fi +} + +sysfs_test_0029() +{ + for delay in 0 2 4 8 16 32 64 128 246 512 1024; do + echo "Using delay-after-completion: $delay" + sysfs_race_kernfs_kernfs_fop_write_iter 0029 at_start 1 $delay + done +} + +sysfs_test_0030() +{ + for delay in 0 2 4 8 16 32 64 128 246 512 1024; do + echo "Using delay-after-completion: $delay" + sysfs_race_kernfs_kernfs_fop_write_iter 0030 before_mutex 1 $delay + done +} + +sysfs_test_0031() +{ + for delay in 0 2 4 8 16 32 64 128 246 512 1024; do + echo "Using delay-after-completion: $delay" + sysfs_race_kernfs_kernfs_fop_write_iter 0031 after_mutex 1 $delay + done +} + +# A write only succeeds *iff* a module removal happens *after* the +# kernfs active reference is obtained with kernfs_get_active(). +sysfs_test_0032() +{ + for delay in 0 2 4 8 16 32 64 128 246 512 1024; do + echo "Using delay-after-completion: $delay" + sysfs_race_kernfs_kernfs_fop_write_iter 0032 after_active 0 $delay + done +} + test_gen_desc() { echo -n "$1 x $(get_test_count $1)" @@ -1013,6 +1184,10 @@ list_tests() echo "$(test_gen_desc 0026) - block test writing y larger delay and resetting device" echo "$(test_gen_desc 0027) - test rmmod deadlock while writing x ... " echo "$(test_gen_desc 0028) - test rmmod deadlock using rtnl_lock while writing x ..." + echo "$(test_gen_desc 0029) - racing removal of store op with kernfs at start" + echo "$(test_gen_desc 0030) - racing removal of store op with kernfs before mutex" + echo "$(test_gen_desc 0031) - racing removal of store op with kernfs after mutex" + echo "$(test_gen_desc 0032) - racing removal of store op with kernfs after active" } usage()