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 2F5CA3BBF0; Wed, 4 Feb 2026 15:00:44 +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=1770217244; cv=none; b=gujgCEHeevlyveAQGryqADh+eJ010evrtFuiTMNFO1qAquUDiIGnHB6v7clqcqkfmAyuKAjtZmGEGzlQZkaZdc/QeRUxWpmIG1ALRpr1ZXz+rIZQtm8HT2e16oVP9wzmuBPGzm0yu4/5AhmLSwnyKe+UDn2brvC6unfCXIezWSU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770217244; c=relaxed/simple; bh=2lnDUk4E3M7SbgyaE/HDRIiDwhMSHHni471Z6zCtM2I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=quZiBlt+NpMkSHb8trDzqNJKSVX2z5oJOfkDxx1VScB7Wr8t/kw5p8rfbRdi7Hs0OSqmkeJ0mn86gKaynjS5/czrkwEsF+VxLlKMsuPTaTAxl6h6/VYqc1F0QK9oW6IkqZdoXmolFpIt1zQZurwXiH4qWBQtvfViunQJUyY814U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FyLwhbjP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FyLwhbjP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 654E4C116C6; Wed, 4 Feb 2026 15:00:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770217244; bh=2lnDUk4E3M7SbgyaE/HDRIiDwhMSHHni471Z6zCtM2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FyLwhbjPrJHlpQeTUyTxGL1boVHTVJIW/gJTasAKiw5wJpHztvMySoHww2Cem5MCF x6hb26/4Vkinn9bCUuk84hklBg7Oy35oM4DA8yc2Jrv5XQ1MCM0HIkQ7FY35xAue/S T3uJ4Aeh/Ah9IfmRjr4WdVkY5loHW2ZJ6JdcnvA4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Matthew Wilcox (Oracle)" , syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com, "David Hildenbrand (Red Hat)" , Zi Yan , Alistair Popple , Byungchul Park , Gregory Price , Jann Horn , Joshua Hahn , Liam Howlett , Lorenzo Stoakes , Matthew Brost , Rakie Kim , Rik van Riel , Vlastimil Babka , Ying Huang , Andrew Morton , Lance Yang Subject: [PATCH 5.15 132/206] migrate: correct lock ordering for hugetlb file folios Date: Wed, 4 Feb 2026 15:39:23 +0100 Message-ID: <20260204143902.952540683@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260204143858.193781818@linuxfoundation.org> References: <20260204143858.193781818@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthew Wilcox (Oracle) commit b7880cb166ab62c2409046b2347261abf701530e upstream. Syzbot has found a deadlock (analyzed by Lance Yang): 1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock). 2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire folio_lock. migrate_pages() -> migrate_hugetlbs() -> unmap_and_move_huge_page() <- Takes folio_lock! -> remove_migration_ptes() -> __rmap_walk_file() -> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)! hugetlbfs_fallocate() -> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)! -> hugetlbfs_zero_partial_page() -> filemap_lock_hugetlb_folio() -> filemap_lock_folio() -> __filemap_get_folio <- Waits for folio_lock! The migration path is the one taking locks in the wrong order according to the documentation at the top of mm/rmap.c. So expand the scope of the existing i_mmap_lock to cover the calls to remove_migration_ptes() too. This is (mostly) how it used to be after commit c0d0381ade79. That was removed by 336bf30eb765 for both file & anon hugetlb pages when it should only have been removed for anon hugetlb pages. Link: https://lkml.kernel.org/r/20260109041345.3863089-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Fixes: 336bf30eb765 ("hugetlbfs: fix anon huge page migration race") Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/68e9715a.050a0220.1186a4.000d.GAE@google.com Debugged-by: Lance Yang Acked-by: David Hildenbrand (Red Hat) Acked-by: Zi Yan Cc: Alistair Popple Cc: Byungchul Park Cc: Gregory Price Cc: Jann Horn Cc: Joshua Hahn Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Brost Cc: Rakie Kim Cc: Rik van Riel Cc: Vlastimil Babka Cc: Ying Huang Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/migrate.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1291,6 +1291,7 @@ static int unmap_and_move_huge_page(new_ struct page *new_hpage; struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; + enum ttu_flags ttu = 0; /* * Migratability of hugepages depends on architectures and their size. @@ -1344,9 +1345,6 @@ static int unmap_and_move_huge_page(new_ goto put_anon; if (page_mapped(hpage)) { - bool mapping_locked = false; - enum ttu_flags ttu = 0; - if (!PageAnon(hpage)) { /* * In shared mappings, try_to_unmap could potentially @@ -1358,15 +1356,11 @@ static int unmap_and_move_huge_page(new_ if (unlikely(!mapping)) goto unlock_put_anon; - mapping_locked = true; ttu |= TTU_RMAP_LOCKED; } try_to_migrate(hpage, ttu); page_was_mapped = 1; - - if (mapping_locked) - i_mmap_unlock_write(mapping); } if (!page_mapped(hpage)) @@ -1374,7 +1368,11 @@ static int unmap_and_move_huge_page(new_ if (page_was_mapped) remove_migration_ptes(hpage, - rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false); + rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, + ttu ? true : false); + + if (ttu & TTU_RMAP_LOCKED) + i_mmap_unlock_write(mapping); unlock_put_anon: unlock_page(new_hpage);