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 2AAFE36D9E9; Sat, 28 Feb 2026 17:57:21 +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=1772301441; cv=none; b=nEUyCb40EmH4jw94i7dz+fHo9jggp89itbFfOmETu7mqRvux7I+SkITa8lrWqaEsE9L8bhEwjTDpa1xfNU5YJ03QjCNj78KQyoevfMsO20JM5icHBfGQT0SZksT5vPIQOj4fJtTAuqpsM9THt46rk+ahWKlmWlr0BdU4h2WCv0I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772301441; c=relaxed/simple; bh=5s8BBKdf4ztkBwOi4i6eDwdPKMgB3eEiCkhMfk7U7/g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kXLw7GemV7YnTP0OImRDGgfHnbY8a9IUM5884CM3FYhR9G3pO0npohgh5/K0l5iWK0Rpt8sXasfReVpvPcIoqcQ6JGylCKCP1wLDfPeyB2aGgQGeS36HJxhmEwHiO4EsFnpsAi138adSaKrgkkiav7UBEawTuSkzeAqmYStXfgU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PgqvI3s4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PgqvI3s4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 397DAC2BC87; Sat, 28 Feb 2026 17:57:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772301441; bh=5s8BBKdf4ztkBwOi4i6eDwdPKMgB3eEiCkhMfk7U7/g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PgqvI3s4uqnL3DfUfiAH4lq2UgquU02rCVyh82FY3zDXPtwSjniftHwAVF1rVQgGc OKei7XXggxwn8tlzRKTXX0C0O0eRtr2ZO/t3wbBnvbMgHVLEh2qPcslTrMGJRBWh2F jR1sIc+Z9KYPXESMRAsLJHXKpWDWlrsHKE+WMf/ACrv+BeVVpXuUU/0JCC99uF6PQu 9LgkIVz5iaepsYPKPUoZLJR5DSfwps84SmqsOBjN9ZNxgPr3Ix3g12moa8YycmvNgQ RJ/GxSKsRDWGC6QPj7eHXJl4e5cDcAg46+ZLNMmuoz0LuPneEdhSSSfv092oohpmLU oCHlaNaErxUOQ== From: Sasha Levin To: patches@lists.linux.dev Cc: Deepanshu Kartikey , syzbot+d8d4c31d40f868eaea30@syzkaller.appspotmail.com, Uladzislau Rezki , Hillf Danton , stable@vger.kernel.org, Andrew Morton , Sasha Levin Subject: [PATCH 6.18 627/752] mm/vmalloc: prevent RCU stalls in kasan_release_vmalloc_node Date: Sat, 28 Feb 2026 12:45:38 -0500 Message-ID: <20260228174750.1542406-627-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228174750.1542406-1-sashal@kernel.org> References: <20260228174750.1542406-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Deepanshu Kartikey [ Upstream commit 5747435e0fd474c24530ef1a6822f47e7d264b27 ] 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 Signed-off-by: Sasha Levin --- mm/vmalloc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 4fbd6e7dc479a..e2f526ad7abba 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2241,11 +2241,14 @@ decay_va_pool_node(struct vmap_node *vn, bool full_decay) 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; @@ -2255,6 +2258,11 @@ kasan_release_vmalloc_node(struct vmap_node *vn) 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); -- 2.51.0