From: Vlastimil Babka Date: Tue, 17 Jan 2023 10:19:39 +0000 (+0100) Subject: mm, mremap: fix mremap() expanding for vma's with vm_ops->close() X-Git-Tag: baikal/aarch64/sdk6.1~40 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=59503d5cbaa86cd918d96b06fb93917e45a32485;p=kernel.git mm, mremap: fix mremap() expanding for vma's with vm_ops->close() commit d014cd7c1c358edc3ea82ebf327a036a42ed0164 upstream. Fabian has reported another regression in 6.1 due to dda05c51364b ("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 dda05c51364b. 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. [akpm@linux-foundation.org: fix indenting whitespace, reflow comment] Link: https://lkml.kernel.org/r/20230117101939.9753-1-vbabka@suse.cz Fixes: dda05c51364b ("mm: add merging after mremap resize") Signed-off-by: Vlastimil Babka Reported-by: Fabian Vogt Link: https://bugzilla.suse.com/show_bug.cgi?id=1206359#c35 Tested-by: Fabian Vogt Cc: Jakub Matěna Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- diff --git a/mm/mremap.c b/mm/mremap.c index fe587c5d65913..930f65c315c02 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -1027,16 +1027,29 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, } /* - * Function vma_merge() is called on the extension we are adding to - * the already existing vma, vma_merge() will merge this extension with - * 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. + * Function vma_merge() is called on the extension we + * are adding to the already existing vma, vma_merge() + * will merge this extension with 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;