From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 97D154B1B53 for ; Thu, 3 Sep 2026 13:53:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788443635; cv=none; b=pks8z+zzqHmhuKFv1gm0pW/bqqdyg3vVE3EgGEumxIdOPf3gmDh53OoAemlt5c1w0o71Dw+HFRdBxslM/4nfQAxEJeoUUP6/GTzH79krHv6i1JRGeDTipmuccA6ozsMu6JyUyQuUguo6oAzGqzJtw+a8hkdGf3dtBDcpcXeuBWI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788443635; c=relaxed/simple; bh=qzxyekJdNyOQYdcEsStq/p+hl+OopOL+upiw6yPRV+g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sIgpEIXso3jlZyzH7MmYk4B6o9LnY1zQHwG5DEcE7KQ76VYyM+7ukmO1LkNZgkZTWQr5LwxiTZHfGdg0M4Uj+SdUQ78TMXp/Js4rwbfZztWU2J0b7qlWIHCb8u6BPh1h2LcmmmrtThJPgZx8mQX6stwyPaTnU8JKS9B4PdyoEAs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lSUKEM83; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lSUKEM83" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B68E1F00A3E; Thu, 3 Sep 2026 13:53:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788443627; bh=Uk0nYgyAOzrLfP+QWaiVXHbXJD3UQau6A89j+atAhes=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lSUKEM83gWEWjW1qvQbhKh8YSCAc5tBchd92UT9dCT6faDWAcssBzYwcURXF4Uso3 xGCTGRltJeo/gqlIuIKAx2L3Rv52+5CcyKSLWdzkA3otMJLeANk3rrB/tF3fTbz1zK +JTkQCKuQJkgUv3Gy2CzVXr0oxzYgadnuqiKmXwE+ozdn8sJysMPYx2+9cZR18W0CO A+/8fuJyl8GHk8/WPbuHydZv14GXqC/c5ghBhcryV/i4XHpgZJNShSUTHirRbFAoRo Q4aMSEoy4NOhNCPphlIuRzUZR7XZk57mNBNGUyDKtCI5XWap+PtilS9z2MVIbiyVbQ maruwW1ujgHfw== From: Sasha Levin To: stable@vger.kernel.org Cc: gao xu , Barry Song , Suren Baghdasaryan , Yosry Ahmed , Andrew Morton , Sasha Levin Subject: [PATCH 6.12.y 1/2] mm: fix possible NULL pointer dereference in __swap_duplicate Date: Thu, 3 Sep 2026 09:53:43 -0400 Message-ID: <20260903135344.780203-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090322-roaming-sherry-27d1@gregkh> References: <2026090322-roaming-sherry-27d1@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: gao xu [ Upstream commit c3e998398de48a7528842f05858a3a6bb21002e6 ] Add a NULL check on the return value of swp_swap_info in __swap_duplicate to prevent crashes caused by NULL pointer dereference. The reason why swp_swap_info() returns NULL is unclear; it may be due to CPU cache issues or DDR bit flips. The probability of this issue is very small - it has been observed to occur approximately 1 in 500,000 times per week. The stack info we encountered is as follows: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058 [RB/E]rb_sreason_str_set: sreason_str set null_pointer Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 39-bit VAs, pgdp=00000008a80e5000 [0000000000000058] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Skip md ftrace buffer dump for: 0x1609e0 ... pc : swap_duplicate+0x44/0x164 lr : copy_page_range+0x508/0x1e78 sp : ffffffc0f2a699e0 x29: ffffffc0f2a699e0 x28: ffffff8a5b28d388 x27: ffffff8b06603388 x26: ffffffdf7291fe70 x25: 0000000000000006 x24: 0000000000100073 x23: 00000000002d2d2f x22: 0000000000000008 x21: 0000000000000000 x20: 00000000002d2d2f x19: 18000000002d2d2f x18: ffffffdf726faec0 x17: 0000000000000000 x16: 0010000000000001 x15: 0040000000000001 x14: 0400000000000001 x13: ff7ffffffffffb7f x12: ffeffffffffffbff x11: ffffff8a5c7e1898 x10: 0000000000000018 x9 : 0000000000000006 x8 : 1800000000000000 x7 : 0000000000000000 x6 : ffffff8057c01f10 x5 : 000000000000a318 x4 : 0000000000000000 x3 : 0000000000000000 x2 : 0000006daf200000 x1 : 0000000000000001 x0 : 18000000002d2d2f Call trace: swap_duplicate+0x44/0x164 copy_page_range+0x508/0x1e78 copy_process+0x1278/0x21cc kernel_clone+0x90/0x438 __arm64_sys_clone+0x5c/0x8c invoke_syscall+0x58/0x110 do_el0_svc+0x8c/0xe0 el0_svc+0x38/0x9c el0t_64_sync_handler+0x44/0xec el0t_64_sync+0x1a8/0x1ac Code: 9139c35a 71006f3f 54000568 f8797b55 (f9402ea8) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception SMP: stopping secondary CPUs The patch seems to only provide a workaround, but there are no more effective software solutions to handle the bit flips problem. This path will change the issue from a system crash to a process exception, thereby reducing the impact on the entire machine. akpm: this is probably a kernel bug, but this patch keeps the system running and doesn't reduce that bug's debuggability. Link: https://lkml.kernel.org/r/e223b0e6ba2f4924984b1917cc717bd5@honor.com Signed-off-by: gao xu Reviewed-by: Barry Song Cc: Suren Baghdasaryan Cc: Yosry Ahmed Signed-off-by: Andrew Morton Stable-dep-of: f9dc428249ed ("mm, swap: ratelimit bad swap entry reports") Signed-off-by: Sasha Levin --- mm/swapfile.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index 47ff0dfefb498..ed4423b198a7b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3665,6 +3665,10 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) int err, i; si = swp_swap_info(entry); + if (WARN_ON_ONCE(!si)) { + pr_err("%s%08lx\n", Bad_file, entry.val); + return -EINVAL; + } offset = swp_offset(entry); VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER); -- 2.53.0