The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 76ba6acfcce871db13ad51c6dc8f56fec2e92853 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024073058-game-plant-575c@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

76ba6acfcce8 ("mm: optimize the redundant loop of mm_update_owner_next()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 76ba6acfcce871db13ad51c6dc8f56fec2e92853 Mon Sep 17 00:00:00 2001 From: Jinliang Zheng alexjlzheng@tencent.com Date: Thu, 20 Jun 2024 20:21:24 +0800 Subject: [PATCH] mm: optimize the redundant loop of mm_update_owner_next()

When mm_update_owner_next() is racing with swapoff (try_to_unuse()) or /proc or ptrace or page migration (get_task_mm()), it is impossible to find an appropriate task_struct in the loop whose mm_struct is the same as the target mm_struct.

If the above race condition is combined with the stress-ng-zombie and stress-ng-dup tests, such a long loop can easily cause a Hard Lockup in write_lock_irq() for tasklist_lock.

Recognize this situation in advance and exit early.

Link: https://lkml.kernel.org/r/20240620122123.3877432-1-alexjlzheng@tencent.com Signed-off-by: Jinliang Zheng alexjlzheng@tencent.com Acked-by: Michal Hocko mhocko@suse.com Cc: Christian Brauner brauner@kernel.org Cc: Jens Axboe axboe@kernel.dk Cc: Mateusz Guzik mjguzik@gmail.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Oleg Nesterov oleg@redhat.com Cc: Tycho Andersen tandersen@netflix.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/kernel/exit.c b/kernel/exit.c index f95a2c1338a8..81fcee45d630 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -484,6 +484,8 @@ void mm_update_next_owner(struct mm_struct *mm) * Search through everything else, we should not get here often. */ for_each_process(g) { + if (atomic_read(&mm->mm_users) <= 1) + break; if (g->flags & PF_KTHREAD) continue; for_each_thread(g, c) {