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Wed, 13 Aug 2025 16:40:59 +0800 From: Gu Bowen To: Catalin Marinas , Andrew Morton CC: , , Waiman Long , Breno Leitao , John Ogness , Lu Jialin , Gu Bowen Subject: [PATCH v3] mm: Fix possible deadlock in console_trylock_spinning Date: Wed, 13 Aug 2025 16:53:10 +0800 Message-ID: <20250813085310.2260586-1-gubowen5@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.67.174.33] X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To kwepemh100007.china.huawei.com (7.202.181.92) X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: EE37580009 X-Stat-Signature: qphro8f7gthab81jecrfxu5cqmtngdh5 X-HE-Tag: 1755074464-559092 X-HE-Meta: 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 QdEEKK1f P1BQpmRFa0Zo9BhWGb6wbUfwfkZJlUJ+XQTI6dua8ffMRda9Eqq0IhBWjf/tjIoV3jt/k2uHazj+mGYx/wruF/8IO5kKJlRACXEs7siVbXOA7aCckrhsHzrK1e0ur0UnRCo1t9b2QAtDpb1Y3Lqs3RBs5eMGSSQgUo0/M93426AR/n/T6kro+GDvNomAzhyFWTkkAUO0VuWQM2QZl6dyLv+DW4CkeRnipxkeucO66HIvF2X/UywEdiOO2uHtb8XRRrrIJFB33lP/6Z2Rtkfa4HqcpAWbCXATNmP+wctTbQEKzcctXM1pMNyi//ZHL5GBDSc6zA8rnDOd1qhxcY7umnP8SkQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Our syztester report the lockdep WARNING [1]. kmemleak_scan_thread() invokes scan_block() which may invoke a nomal printk() to print warning message. This can cause a deadlock in the scenario reported below: CPU0 CPU1 ---- ---- lock(kmemleak_lock); lock(&port->lock); lock(kmemleak_lock); lock(console_owner); To solve this problem, switch to printk_safe mode before printing warning message, this will redirect all printk()-s to a special per-CPU buffer, which will be flushed later from a safe context (irq work), and this deadlock problem can be avoided. The proper API to use should be printk_deferred_enter()/printk_deferred_exit() if we want to deferred the printing [2]. This patch also fixes other similar case that need to use the printk deferring [3]. [1] https://lore.kernel.org/all/20250730094914.566582-1-gubowen5@huawei.com/ [2] https://lore.kernel.org/all/5ca375cd-4a20-4807-b897-68b289626550@redhat.com/ [3] https://lore.kernel.org/all/aJCir5Wh362XzLSx@arm.com/ ==================== Cc: stable@vger.kernel.org # 5.10 Signed-off-by: Gu Bowen --- mm/kmemleak.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 4801751cb6b6..b9cb321c1cf3 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -390,9 +390,15 @@ static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) else if (object->pointer == ptr || alias) return object; else { + /* + * Printk deferring due to the kmemleak_lock held. + * This is done to avoid deadlock. + */ + printk_deferred_enter(); kmemleak_warn("Found object by alias at 0x%08lx\n", ptr); dump_object_info(object); + printk_deferred_exit(); break; } } @@ -632,6 +638,11 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, else if (parent->pointer + parent->size <= ptr) link = &parent->rb_node.rb_right; else { + /* + * Printk deferring due to the kmemleak_lock held. + * This is done to avoid deadlock. + */ + printk_deferred_enter(); kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)\n", ptr); /* @@ -639,6 +650,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, * be freed while the kmemleak_lock is held. */ dump_object_info(parent); + printk_deferred_exit(); kmem_cache_free(object_cache, object); object = NULL; goto out; -- 2.25.1