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 AE26D4FB9AB; Sat, 5 Sep 2026 18:48:22 +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=1788634104; cv=none; b=X3xMGK2uCxr83bY6XLXqlMhoxKYQW2ARXyyhSBZkt09/O9QxPW0DeEEncwOIKYn/IFIBsDAeYyhmtuy2Vh3vkPJME12azFgO1dPVe1uD4mOZp37gzetyr3BPcsLxEPSHicWm92C3z2i7rHm6vTL1kDBbiWoje0Br6HLyjd37kuM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788634104; c=relaxed/simple; bh=BuA27QtOlNIuzQaTeIL+gZbhxt57kF7m96mqOUoGiRk=; h=Date:To:From:Subject:Message-Id; b=okKCF2k2HQWOwqBFKMsi2Q+gsXPLMFMnS5F2r3/oV1AGDud5Ne8xTDgII4g3r3+6fRvvnyfW/MJApkt/NgBy5MijvR65UkcG4OoAGJvLkGp8sYJ9jmuWmt1k9YGSYZ+zWVHnRyZ+p+a+W7ki2hzacApKzHi/SWnCT5OyLuHlXgw= 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=dh9jR4PB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="dh9jR4PB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6D671F00A3A; Sat, 5 Sep 2026 18:48:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788634102; bh=WZGHa5+KAm7P6Gm0hh1/j/Sjus8CSwkO3xyWmLtdEmg=; h=Date:To:From:Subject; b=dh9jR4PBOOPhiryezs1NHfNg8JCW8y7qU3jCsAkLYO71Z/J6phi+dhS4yrxqxIsT8 iAkErJ5IYRA9qSDx13KMkNmncu5DUqsRFXDvv5qf7y+gUmMdHVDeRB0miAc1oJK4Ag x/z0IU3idw6vg8QheNqXdELobSxGGA8dQ//u3L8s= Date: Sat, 05 Sep 2026 11:48:21 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,viro@zeniv.linux.org.uk,stable@vger.kernel.org,jack@suse.cz,cinereal@riseup.net,brauner@kernel.org,apopple@nvidia.com,seunguk.shin@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] fs-dax-check-zero-or-empty-entry-before-converting-xarray-entry.patch removed from -mm tree Message-Id: <20260905184821.D6D671F00A3A@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: fs/dax: check zero or empty entry before converting xarray entry has been removed from the -mm tree. Its filename was fs-dax-check-zero-or-empty-entry-before-converting-xarray-entry.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Seunguk Shin Subject: fs/dax: check zero or empty entry before converting xarray entry Date: Mon, 03 Aug 2026 13:34:55 +0100 Calling dax_to_folio() with empty entry causes kernel panic below when booting a VM with DAX enabled storage. This patch checks empty entry before calling dax_to_folio() on dax_associate_entry(), dax_disassociate_entry(), and dax_busy_page(). Commit 98c183a4fccf ("fs/dax: don't disassociate zero page entries") added guards in the associate and disassociate paths, but the guards still come after dax_to_folio(), and dax_busy_page() still has the same problem. [ 0.737679] EXT4-fs (pmem0p1): mounted filesystem 79676804-7c8b-491a-b2a6-9bae3c72af70 ro with ordered data mode. Quota mode: disabled. [ 0.737891] VFS: Mounted root (ext4 filesystem) readonly on device 259:1. [ 0.739119] devtmpfs: mounted [ 0.739476] Freeing unused kernel memory: 1920K [ 0.740156] Run /sbin/init as init process [ 0.740229] with arguments: [ 0.740286] /sbin/init [ 0.740321] with environment: [ 0.740369] HOME=/ [ 0.740400] TERM=linux [ 0.743162] Unable to handle kernel paging request at virtual address fffffdffbf000008 [ 0.743285] Mem abort info: [ 0.743316] ESR = 0x0000000096000006 [ 0.743371] EC = 0x25: DABT (current EL), IL = 32 bits [ 0.743444] SET = 0, FnV = 0 [ 0.743489] EA = 0, S1PTW = 0 [ 0.743545] FSC = 0x06: level 2 translation fault [ 0.743610] Data abort info: [ 0.743656] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 [ 0.743720] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 0.743785] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 0.743848] swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000000b9d17000 [ 0.743931] [fffffdffbf000008] pgd=10000000bfa3d403, p4d=10000000bfa3d403, pud=1000000040bfe403, pmd=0000000000000000 [ 0.744070] Internal error: Oops: 0000000096000006 [#1] SMP [ 0.748888] CPU: 0 UID: 0 PID: 1 Comm: init Not tainted 6.18.4 #1 NONE [ 0.749421] pstate: 004000c5 (nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 0.749969] pc : dax_disassociate_entry.constprop.0+0x20/0x50 [ 0.750444] lr : dax_insert_entry+0xcc/0x408 [ 0.750802] sp : ffff80008000b9e0 [ 0.751083] x29: ffff80008000b9e0 x28: 0000000000000000 x27: 0000000000000000 [ 0.751682] x26: 0000000001963d01 x25: ffff0000004f7d90 x24: 0000000000000000 [ 0.752264] x23: 0000000000000000 x22: ffff80008000bcc8 x21: 0000000000000011 [ 0.752836] x20: ffff80008000ba90 x19: 0000000001963d01 x18: 0000000000000000 [ 0.753407] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 [ 0.753970] x14: ffffbf3154b9ae70 x13: 0000000000000000 x12: ffffbf3154b9ae70 [ 0.754548] x11: ffffffffffffffff x10: 0000000000000000 x9 : 0000000000000000 [ 0.755122] x8 : 000000000000000d x7 : 000000000000001f x6 : 0000000000000000 [ 0.755707] x5 : 0000000000000000 x4 : 0000000000000000 x3 : fffffdffc0000000 [ 0.756287] x2 : 0000000000000008 x1 : 0000000040000000 x0 : fffffdffbf000000 [ 0.756871] Call trace: [ 0.757107] dax_disassociate_entry.constprop.0+0x20/0x50 (P) [ 0.757592] dax_iomap_pte_fault+0x4fc/0x808 [ 0.757951] dax_iomap_fault+0x28/0x30 [ 0.758258] ext4_dax_huge_fault+0x80/0x2dc [ 0.758594] ext4_dax_fault+0x10/0x3c [ 0.758892] __do_fault+0x38/0x12c [ 0.759175] __handle_mm_fault+0x530/0xcf0 [ 0.759518] handle_mm_fault+0xe4/0x230 [ 0.759833] do_page_fault+0x17c/0x4dc [ 0.760144] do_translation_fault+0x30/0x38 [ 0.760483] do_mem_abort+0x40/0x8c [ 0.760771] el0_ia+0x4c/0x170 [ 0.761032] el0t_64_sync_handler+0xd8/0xdc [ 0.761371] el0t_64_sync+0x168/0x16c [ 0.761677] Code: f9453021 f2dfbfe3 cb813080 8b001860 (f9400401) [ 0.762168] ---[ end trace 0000000000000000 ]--- [ 0.762550] note: init[1] exited with irqs disabled [ 0.762631] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b Link: https://lore.kernel.org/m2y0enxtzk.fsf@arm.com Fixes: 38607c62b34b ("fs/dax: properly refcount fs dax pages") Signed-off-by: Seunguk Shin Reviewed-by: Jan Kara Reviewed-by: Alistair Popple Reported-by: Kiara Grouwstra Cc: Al Viro Cc: Christian Brauner Cc: Matthew Wilcox (Oracle) Cc: Signed-off-by: Andrew Morton --- fs/dax.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/fs/dax.c~fs-dax-check-zero-or-empty-entry-before-converting-xarray-entry +++ a/fs/dax.c @@ -480,11 +480,12 @@ static void dax_associate_entry(void *en unsigned long address, bool shared) { unsigned long size = dax_entry_size(entry), index; - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return; + folio = dax_to_folio(entry); index = linear_page_index(vma, address & ~(size - 1)); if (shared && (folio->mapping || dax_folio_is_shared(folio))) { if (folio->mapping) @@ -505,21 +506,23 @@ static void dax_associate_entry(void *en static void dax_disassociate_entry(void *entry, struct address_space *mapping, bool trunc) { - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return; + folio = dax_to_folio(entry); dax_folio_put(folio); } static struct page *dax_busy_page(void *entry) { - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return NULL; + folio = dax_to_folio(entry); if (folio_ref_count(folio) - folio_mapcount(folio)) return &folio->page; else _ Patches currently in -mm which might be from seunguk.shin@arm.com are