From: Rongwei Wang rongwei.wang@linux.alibaba.com Subject: 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 ---
fs/open.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/fs/open.c~mm-thp-fix-incorrect-unmap-behavior-for-private-pages +++ a/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); } } _