The patch below does not apply to the 5.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8468e937df1f31411d1e127fa38db064af051fe5 Mon Sep 17 00:00:00 2001

From: Rongwei Wang rongwei.wang@linux.alibaba.com Date: Fri, 5 Nov 2021 13:43:44 -0700 Subject: [PATCH] mm, thp: fix incorrect unmap behavior for private pages

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@linux.alibaba.... Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") Signed-off-by: Rongwei Wang rongwei.wang@linux.alibaba.com Tested-by: Xu Yu xuyu@linux.alibaba.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Song Liu song@kernel.org Cc: William Kucharski william.kucharski@oracle.com Cc: Hugh Dickins hughd@google.com Cc: Yang Shi shy828301@gmail.com Cc: Mike Kravetz mike.kravetz@oracle.com Cc: Collin Fijalkovich cfijalkovich@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/fs/open.c b/fs/open.c index 9ec3cfca3b1a..e0df1536eb69 100644 --- 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); } }