From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 919523191D2; Tue, 27 Jan 2026 04:04:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769486693; cv=none; b=AtBlsjA7/tQo7U/OuC49Ixu2be+swonywweYchd75gd1bwIdMz6x2BFn9+q5vsMAimAbTrRMIMt3xBoseK87HHwsnHI1qrAwdZYEt5NyU2zqB9Qn9SCvceZM1K4EhPb4HaQw5Je4XMap2OWT86Qa2kMD4XH9NVAillHBKLCNFvA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769486693; c=relaxed/simple; bh=wt8QP+/D3ntBtKipjWyeYkn/ZCLF8LRN2iTuJsbrkfk=; h=Date:To:From:Subject:Message-Id; b=gJLwFfYYyMATHzDnvxu8XbBom01ebyEonhpCWO9j+SJV+K1nzCcc2mmDJscWX8WXuFeFkhA/LAmHINmVrZhNnk277kx5ybQfgmDHF/wDcstBprhPR+cMbg56y93lhb4OWhVRmjmjsmfBCCxlK06+biUSQixfYndhsAX+i3bU4fE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=hmeafQuG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="hmeafQuG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61BE9C116C6; Tue, 27 Jan 2026 04:04:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1769486693; bh=wt8QP+/D3ntBtKipjWyeYkn/ZCLF8LRN2iTuJsbrkfk=; h=Date:To:From:Subject:From; b=hmeafQuGQlJ/wbIj6mMAqCnqIpR1XlzWG2X2DdVpltHnNwqJuMvZ3PGcnLzmRgduh ieYn7LB2QaBX5cirvYzlfkNj1IEEazAP/m0doZjb9Hvy+PV11iWhSTmVnf0SyEgkd1 GxeVH5YZuH86qpPCJsYsp9THoXDHOaVALHe8/rN0= Date: Mon, 26 Jan 2026 20:04:52 -0800 To: mm-commits@vger.kernel.org,urezki@gmail.com,stable@vger.kernel.org,hdanton@sina.com,kartikey406@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-vmalloc-prevent-rcu-stalls-in-kasan_release_vmalloc_node.patch removed from -mm tree Message-Id: <20260127040453.61BE9C116C6@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/vmalloc: prevent RCU stalls in kasan_release_vmalloc_node has been removed from the -mm tree. Its filename was mm-vmalloc-prevent-rcu-stalls-in-kasan_release_vmalloc_node.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Deepanshu Kartikey Subject: mm/vmalloc: prevent RCU stalls in kasan_release_vmalloc_node Date: Mon, 12 Jan 2026 16:06:12 +0530 When CONFIG_PAGE_OWNER is enabled, freeing KASAN shadow pages during vmalloc cleanup triggers expensive stack unwinding that acquires RCU read locks. Processing a large purge_list without rescheduling can cause the task to hold CPU for extended periods (10+ seconds), leading to RCU stalls and potential OOM conditions. The issue manifests in purge_vmap_node() -> kasan_release_vmalloc_node() where iterating through hundreds or thousands of vmap_area entries and freeing their associated shadow pages causes: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6229/1:b..l ... task:kworker/0:17 state:R running task stack:28840 pid:6229 ... kasan_release_vmalloc_node+0x1ba/0xad0 mm/vmalloc.c:2299 purge_vmap_node+0x1ba/0xad0 mm/vmalloc.c:2299 Each call to kasan_release_vmalloc() can free many pages, and with page_owner tracking, each free triggers save_stack() which performs stack unwinding under RCU read lock. Without yielding, this creates an unbounded RCU critical section. Add periodic cond_resched() calls within the loop to allow: - RCU grace periods to complete - Other tasks to run - Scheduler to preempt when needed The fix uses need_resched() for immediate response under load, with a batch count of 32 as a guaranteed upper bound to prevent worst-case stalls even under light load. Link: https://lkml.kernel.org/r/20260112103612.627247-1-kartikey406@gmail.com Signed-off-by: Deepanshu Kartikey Reported-by: syzbot+d8d4c31d40f868eaea30@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d8d4c31d40f868eaea30 Link: https://lore.kernel.org/all/20260112084723.622910-1-kartikey406@gmail.com/T/ [v1] Suggested-by: Uladzislau Rezki Reviewed-by: Uladzislau Rezki (Sony) Cc: Hillf Danton Cc: Signed-off-by: Andrew Morton --- mm/vmalloc.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/vmalloc.c~mm-vmalloc-prevent-rcu-stalls-in-kasan_release_vmalloc_node +++ a/mm/vmalloc.c @@ -2273,11 +2273,14 @@ decay_va_pool_node(struct vmap_node *vn, reclaim_list_global(&decay_list); } +#define KASAN_RELEASE_BATCH_SIZE 32 + static void kasan_release_vmalloc_node(struct vmap_node *vn) { struct vmap_area *va; unsigned long start, end; + unsigned int batch_count = 0; start = list_first_entry(&vn->purge_list, struct vmap_area, list)->va_start; end = list_last_entry(&vn->purge_list, struct vmap_area, list)->va_end; @@ -2287,6 +2290,11 @@ kasan_release_vmalloc_node(struct vmap_n kasan_release_vmalloc(va->va_start, va->va_end, va->va_start, va->va_end, KASAN_VMALLOC_PAGE_RANGE); + + if (need_resched() || (++batch_count >= KASAN_RELEASE_BATCH_SIZE)) { + cond_resched(); + batch_count = 0; + } } kasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH); _ Patches currently in -mm which might be from kartikey406@gmail.com are