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 1187A26A0F6; Thu, 22 May 2025 22:10:09 +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=1747951810; cv=none; b=P8J/RkndN1E3tAYqpRLEKU3nBTr7rd5AIQqNWQMaU7/WOyjba68hZE1uTvNpxnwqhMGVwB9VGgJfrw0e082vYlICae8lYpl1NUMQhzwZTAXqLSq9Q6qAdALdzyT+a5JylqIDIJ6I6gyJApezj5DeR9d6vkFR6UJSyzks5pjWorU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747951810; c=relaxed/simple; bh=dXTYcC4RYMGN2fdM3NbtSp+tXzTSTWld932ILimsJS4=; h=Date:To:From:Subject:Message-Id; b=umCck701sj428C8SQV8aRS7eN6jkhY1TkvsYBMzf+E84l7tt8rFWE/Ag0SeF4mq8y8PI+jz7DD/ZCYgcJ+oPhuVksz2tNPu1vrJwMj2tW72ORy4hS2JrCTnEHbTWy8bul14eWvNsJPCwqxtBd1j5F9S5wsUd6d7oLk8crzBxZAQ= 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=ofiNd/dk; 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="ofiNd/dk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CB46C4CEEB; Thu, 22 May 2025 22:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1747951809; bh=dXTYcC4RYMGN2fdM3NbtSp+tXzTSTWld932ILimsJS4=; h=Date:To:From:Subject:From; b=ofiNd/dk4myOvW2F/3yFBls88VOh95Ih6SkGatXFM9XI3/mDF+cuJF55wTXwX6uOH LAEkquMr2YY07tkdoTIZNdowA2VxeV3g8a62grpcYCBRIxXllolDAuPiiV/sTwgmOU LJohsreeijkmlBRPwOcHUH/H+uNUDI+v3ZrWRcAQ= Date: Thu, 22 May 2025 15:10:08 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,osalvador@suse.de,muchun.song@linux.dev,david@redhat.com,baolin.wang@linux.alibaba.com,21cnbao@gmail.com,yangge1116@126.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-hugetlb-fix-kernel-null-pointer-dereference-when-replacing-free-hugetlb-folios.patch added to mm-hotfixes-unstable branch Message-Id: <20250522221009.6CB46C4CEEB@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-hugetlb-fix-kernel-null-pointer-dereference-when-replacing-free-hugetlb-folios.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-fix-kernel-null-pointer-dereference-when-replacing-free-hugetlb-folios.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Ge Yang Subject: mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios Date: Thu, 22 May 2025 11:22:17 +0800 A kernel crash was observed when replacing free hugetlb folios: BUG: kernel NULL pointer dereference, address: 0000000000000028 PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 28 UID: 0 PID: 29639 Comm: test_cma.sh Tainted 6.15.0-rc6-zp #41 PREEMPT(voluntary) RIP: 0010:alloc_and_dissolve_hugetlb_folio+0x1d/0x1f0 RSP: 0018:ffffc9000b30fa90 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000342cca RCX: ffffea0043000000 RDX: ffffc9000b30fb08 RSI: ffffea0043000000 RDI: 0000000000000000 RBP: ffffc9000b30fb20 R08: 0000000000001000 R09: 0000000000000000 R10: ffff88886f92eb00 R11: 0000000000000000 R12: ffffea0043000000 R13: 0000000000000000 R14: 00000000010c0200 R15: 0000000000000004 FS: 00007fcda5f14740(0000) GS:ffff8888ec1d8000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3: 0000000391402000 CR4: 0000000000350ef0 Call Trace: replace_free_hugepage_folios+0xb6/0x100 alloc_contig_range_noprof+0x18a/0x590 ? srso_return_thunk+0x5/0x5f ? down_read+0x12/0xa0 ? srso_return_thunk+0x5/0x5f cma_range_alloc.constprop.0+0x131/0x290 __cma_alloc+0xcf/0x2c0 cma_alloc_write+0x43/0xb0 simple_attr_write_xsigned.constprop.0.isra.0+0xb2/0x110 debugfs_attr_write+0x46/0x70 full_proxy_write+0x62/0xa0 vfs_write+0xf8/0x420 ? srso_return_thunk+0x5/0x5f ? filp_flush+0x86/0xa0 ? srso_return_thunk+0x5/0x5f ? filp_close+0x1f/0x30 ? srso_return_thunk+0x5/0x5f ? do_dup2+0xaf/0x160 ? srso_return_thunk+0x5/0x5f ksys_write+0x65/0xe0 do_syscall_64+0x64/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e There is a potential race between __update_and_free_hugetlb_folio() and replace_free_hugepage_folios(): CPU1 CPU2 __update_and_free_hugetlb_folio replace_free_hugepage_folios folio_test_hugetlb(folio) -- It's still hugetlb folio. __folio_clear_hugetlb(folio) hugetlb_free_folio(folio) h = folio_hstate(folio) -- Here, h is NULL pointer When the above race condition occurs, folio_hstate(folio) returns NULL, and subsequent access to this NULL pointer will cause the system to crash. To resolve this issue, execute folio_hstate(folio) under the protection of the hugetlb_lock lock, ensuring that folio_hstate(folio) does not return NULL. Link: https://lkml.kernel.org/r/1747884137-26685-1-git-send-email-yangge1116@126.com Fixes: 04f13d241b8b ("mm: replace free hugepage folios after migration") Signed-off-by: Ge Yang Reviewed-by: Muchun Song Reviewed-by: Oscar Salvador Cc: Baolin Wang Cc: Barry Song <21cnbao@gmail.com> Cc: David Hildenbrand Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/hugetlb.c~mm-hugetlb-fix-kernel-null-pointer-dereference-when-replacing-free-hugetlb-folios +++ a/mm/hugetlb.c @@ -2949,12 +2949,20 @@ int replace_free_hugepage_folios(unsigne while (start_pfn < end_pfn) { folio = pfn_folio(start_pfn); + + /* + * The folio might have been dissolved from under our feet, so make sure + * to carefully check the state under the lock. + */ + spin_lock_irq(&hugetlb_lock); if (folio_test_hugetlb(folio)) { h = folio_hstate(folio); } else { + spin_unlock_irq(&hugetlb_lock); start_pfn++; continue; } + spin_unlock_irq(&hugetlb_lock); if (!folio_ref_count(folio)) { ret = alloc_and_dissolve_hugetlb_folio(h, folio, _ Patches currently in -mm which might be from yangge1116@126.com are mm-hugetlb-fix-kernel-null-pointer-dereference-when-replacing-free-hugetlb-folios.patch