This is a note to let you know that I've just added the patch titled mm, thp: fix incorrect unmap behavior for private pages to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-thp-fix-incorrect-unmap-behavior-for-private-pages.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 8468e937df1f31411d1e127fa38db064af051fe5 Mon Sep 17 00:00:00 2001 From: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> Date: Fri, 5 Nov 2021 13:43:44 -0700 Subject: mm, thp: fix incorrect unmap behavior for private pages From: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> commit 8468e937df1f31411d1e127fa38db064af051fe5 upstream. When truncating pagecache on file THP, the private pages of a process should not be unmapped mapping. This incorrect behavior on a dynamic shared libraries which will cause related processes to happen core dump. A simple test for a DSO (Prerequisite is the DSO mapped in file THP): int main(int argc, char *argv[]) { int fd; fd = open(argv[1], O_WRONLY); if (fd < 0) { perror("open"); } close(fd); return 0; } The test only to open a target DSO, and do nothing. But this operation will lead one or more process to happen core dump. This patch mainly to fix this bug. Link: https://lkml.kernel.org/r/20211025092134.18562-3-rongwei.wang@xxxxxxxxxxxxxxxxx Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") Signed-off-by: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> Tested-by: Xu Yu <xuyu@xxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Song Liu <song@xxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Collin Fijalkovich <cfijalkovich@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/open.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/fs/open.c +++ b/fs/open.c @@ -857,8 +857,17 @@ static int do_dentry_open(struct file *f */ smp_mb(); if (filemap_nr_thps(inode->i_mapping)) { + struct address_space *mapping = inode->i_mapping; + filemap_invalidate_lock(inode->i_mapping); - truncate_pagecache(inode, 0); + /* + * unmap_mapping_range just need to be called once + * here, because the private pages is not need to be + * unmapped mapping (e.g. data segment of dynamic + * shared libraries here). + */ + unmap_mapping_range(mapping, 0, 0, 0); + truncate_inode_pages(mapping, 0); filemap_invalidate_unlock(inode->i_mapping); } } Patches currently in stable-queue which might be from rongwei.wang@xxxxxxxxxxxxxxxxx are queue-5.15/mm-thp-fix-incorrect-unmap-behavior-for-private-pages.patch queue-5.15/mm-thp-lock-filemap-when-truncating-page-cache.patch