From: Wander Lairson Costa wander@redhat.com

mainline inclusion from mainline-v6.10-rc5 commit b58652db66c910c2245f5bee7deca41c12d707b9 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGEN4 CVE: CVE-2024-41023

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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During the execution of the following stress test with linux-rt:

stress-ng --cyclic 30 --timeout 30 --minimize --quiet

kmemleak frequently reported a memory leak concerning the task_struct:

unreferenced object 0xffff8881305b8000 (size 16136): comm "stress-ng", pid 614, jiffies 4294883961 (age 286.412s) object hex dump (first 32 bytes): 02 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .@.............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ debug hex dump (first 16 bytes): 53 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 S............... backtrace: [<00000000046b6790>] dup_task_struct+0x30/0x540 [<00000000c5ca0f0b>] copy_process+0x3d9/0x50e0 [<00000000ced59777>] kernel_clone+0xb0/0x770 [<00000000a50befdc>] __do_sys_clone+0xb6/0xf0 [<000000001dbf2008>] do_syscall_64+0x5d/0xf0 [<00000000552900ff>] entry_SYSCALL_64_after_hwframe+0x6e/0x76

The issue occurs in start_dl_timer(), which increments the task_struct reference count and sets a timer. The timer callback, dl_task_timer, is supposed to decrement the reference count upon expiration. However, if enqueue_task_dl() is called before the timer expires and cancels it, the reference count is not decremented, leading to the leak.

This patch fixes the reference leak by ensuring the task_struct reference count is properly decremented when the timer is canceled.

Fixes: feff2e65efd8 ("sched/deadline: Unthrottle PI boosted threads while enqueuing") Signed-off-by: Wander Lairson Costa wander@redhat.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Juri Lelli juri.lelli@redhat.com Link: https://lore.kernel.org/r/20240620125618.11419-1-wander@redhat.com Conflicts: kernel/sched/deadline.c [remove !dl_server(&p->dl) condition] Signed-off-by: Zheng Zucheng zhengzucheng@huawei.com --- kernel/sched/deadline.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 71b55d9de2d9..cff58dba27ff 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1528,8 +1528,12 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) * The replenish timer needs to be canceled. No * problem if it fires concurrently: boosted threads * are ignored in dl_task_timer(). + * + * If the timer callback was running (hrtimer_try_to_cancel == -1), + * it will eventually call put_task_struct(). */ - hrtimer_try_to_cancel(&p->dl.dl_timer); + if (hrtimer_try_to_cancel(&p->dl.dl_timer) == 1) + put_task_struct(p); p->dl.dl_throttled = 0; } } else if (!dl_prio(p->normal_prio)) {