The patch titled Subject: mm, mremap: fix mremap() expanding for vma's with vm_ops->close() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-mremap-fix-mremap-expanding-for-vmas-with-vm_ops-close.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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: Vlastimil Babka vbabka@suse.cz Subject: mm, mremap: fix mremap() expanding for vma's with vm_ops->close() Date: Tue, 17 Jan 2023 11:19:39 +0100

Fabian has reported another regression in 6.1 due to ca3d76b0aa80 ("mm: add merging after mremap resize"). The problem is that vma_merge() can fail when vma has a vm_ops->close() method, causing is_mergeable_vma() test to be negative. This was happening for vma mapping a file from fuse-overlayfs, which does have the method. But when we are simply expanding the vma, we never remove it due to the "merge" with the added area, so the test should not prevent the expansion.

As a quick fix, check for such vmas and expand them using vma_adjust() directly as was done before commit ca3d76b0aa80. For a more robust long term solution we should try to limit the check for vma_ops->close only to cases that actually result in vma removal, so that no merge would be prevented unnecessarily.

Link: https://lkml.kernel.org/r/20230117101939.9753-1-vbabka@suse.cz Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize") Signed-off-by: Vlastimil Babka vbabka@suse.cz Reported-by: Fabian Vogt fvogt@suse.com Link: https://bugzilla.suse.com/show_bug.cgi?id=1206359#c35 Tested-by: Fabian Vogt fvogt@suse.com Cc: Jakub Mat��na matenajakub@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

--- a/mm/mremap.c~mm-mremap-fix-mremap-expanding-for-vmas-with-vm_ops-close +++ a/mm/mremap.c @@ -1032,11 +1032,22 @@ SYSCALL_DEFINE5(mremap, unsigned long, a * the already existing vma (expand operation itself) and possibly also * with the next vma if it becomes adjacent to the expanded vma and * otherwise compatible. + * + * However, vma_merge() can currently fail due to is_mergeable_vma() + * check for vm_ops->close (see the comment there). Yet this should not + * prevent vma expanding, so perform a simple expand for such vma. + * Ideally the check for close op should be only done when a vma would + * be actually removed due to a merge. */ - vma = vma_merge(mm, vma, extension_start, extension_end, + if (!vma->vm_ops || !vma->vm_ops->close) { + vma = vma_merge(mm, vma, extension_start, extension_end, vma->vm_flags, vma->anon_vma, vma->vm_file, extension_pgoff, vma_policy(vma), vma->vm_userfaultfd_ctx, anon_vma_name(vma)); + } else if (vma_adjust(vma, vma->vm_start, addr + new_len, + vma->vm_pgoff, NULL)) { + vma = NULL; + } if (!vma) { vm_unacct_memory(pages); ret = -ENOMEM; _

Patches currently in -mm which might be from vbabka@suse.cz are

revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch mm-mremap-fix-mremap-expanding-for-vmas-with-vm_ops-close.patch