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.
Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs")
Cc: <stable@xxxxxxxxxxxxxxx>
Tested-by: Xu Yu <xuyu@xxxxxxxxxxxxxxxxx>
Signed-off-by: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx>
---
fs/open.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/open.c b/fs/open.c
index e73bf88e5060..f732fb94600c 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);
}
}
--
2.27.0
