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 23DE629B781; Tue, 15 Sep 2026 03:05:45 +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=1789441547; cv=none; b=YapURz4/2jOllMbABkSkiM0VZbScM8fXbOSO4bgKF2Qwnk+dfT7WjKCTknzO8HktaKer+m6KkwASYV2TVwEs+hXdqacKs6iQCQPljKroopCir9scERN18EKpuAAedktg7AyTYeEQlGb2/8znuyT8kIZXSyBSSl7bQYqEOQtzBvY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789441547; c=relaxed/simple; bh=oNMZ+cto2HL7E+zVkc3wNKhPJT/lNVzeq9twaDd7Nj0=; h=Date:To:From:Subject:Message-Id; b=IjNCbUb+YOcnhaK/n5Poc1MoNknrENDeG/pIiLLn881DsbQppgIx6NAWYfkd/vYZzQE6LPbSsQvidi2Qo4Pm+6USs+rhYN3M3PnaGEkMXfLJExuc0UPwPGxtRO76sZhDYwASqHtOPIOYoaCREe/k84HbIpeStlfdbltfiEtsDjs= 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=r+asy+RY; 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="r+asy+RY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8ECF41F000FF; Tue, 15 Sep 2026 03:05:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789441545; bh=CEALWbmZ9Qia7fbPhEJK3QzWRT6Hur9KW+VXqkxpBaU=; h=Date:To:From:Subject; b=r+asy+RY+42X5PuFyaaX3JquyPgw3d2JB0kkd9wBvPBKvAKk49qZYDliD0Huc20E5 gs4aMl8MDANeuN/mHXTbygQYuoo3+Z8s00/dNL0sMT9YoYGJ6J8o7zzP/iqpJmiL1w Ey45SWVKErLB6UamcjNz8RTZibY+/SCUylL4KAC4= Date: Mon, 14 Sep 2026 20:05:45 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,osalvador@suse.de,muchun.song@linux.dev,johan@kernel.org,david@kernel.org,jaewook376@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-hugetlb-preserve-mremap-address-delta-when-skipping-page-tables.patch added to mm-hotfixes-unstable branch Message-Id: <20260915030545.8ECF41F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/hugetlb: preserve mremap address delta when skipping page tables has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-hugetlb-preserve-mremap-address-delta-when-skipping-page-tables.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-preserve-mremap-address-delta-when-skipping-page-tables.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 various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Jaewook You Subject: mm/hugetlb: preserve mremap address delta when skipping page tables Date: Mon, 14 Sep 2026 22:23:52 +0900 move_hugetlb_page_tables() optimizes mremap() by advancing to the last entry in the page table when the source page table does not exist, either initially or after unsharing a PMD table. The common loop increment then steps to the first entry in the next page table. However, the code advances both the source and destination addresses to the last entries in their respective page tables, which is wrong. The destination address must be advanced only by the same amount as the source address. If the source and destination offsets within their page tables differ, the destination address can be advanced too far, causing follow-up issues. Fix this by advancing the destination address by the source advance distance. With a reproducer, we were able to trigger a kernel panic on x86-64. With this fix in place, we can no longer reproduce the issue. Link: https://lore.kernel.org/20260914132352.472-1-jaewook376@gmail.com Fixes: e95a9851787b ("hugetlb: skip to end of PT page mapping when pte not present") Fixes: 4ddb4d91b82f ("hugetlb: do not update address in huge_pmd_unshare") Signed-off-by: Jaewook You Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Cc: Johan Hovold Cc: Muchun Song Cc: Oscar Salvador Cc: Assisted-by: LLM --- mm/hugetlb.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/mm/hugetlb.c~mm-hugetlb-preserve-mremap-address-delta-when-skipping-page-tables +++ a/mm/hugetlb.c @@ -5181,18 +5181,21 @@ int move_hugetlb_page_tables(struct vm_a hugetlb_vma_lock_write(vma); i_mmap_lock_write(mapping); for (; old_addr < old_end; old_addr += sz, new_addr += sz) { + const unsigned long offset_to_last_entry = + (old_addr | last_addr_mask) - old_addr; + src_pte = hugetlb_walk(vma, old_addr, sz); if (!src_pte) { - old_addr |= last_addr_mask; - new_addr |= last_addr_mask; + old_addr += offset_to_last_entry; + new_addr += offset_to_last_entry; continue; } if (huge_pte_none(huge_ptep_get(mm, old_addr, src_pte))) continue; if (huge_pmd_unshare(&tlb, vma, old_addr, src_pte)) { - old_addr |= last_addr_mask; - new_addr |= last_addr_mask; + old_addr += offset_to_last_entry; + new_addr += offset_to_last_entry; continue; } _ Patches currently in -mm which might be from jaewook376@gmail.com are mm-hugetlb-preserve-mremap-address-delta-when-skipping-page-tables.patch