From: Amir Goldstein <amir73il@gmail.com>
Date: Thu, 11 Oct 2018 17:38:14 +0300
Subject: vfs: fix FIGETBSZ ioctl on an overlayfs file
Git-commit: 8f97d1e99149a7f1aa19e47a51b09764382a482e
Patch-mainline: v4.20-rc1
References: bsc#1178202

Some anon_bdev filesystems (e.g. overlayfs, ceph) don't have s_blocksize
set. Returning zero from FIGETBSZ ioctl results in a Floating point
exception from the e2fsprogs utility filefrag, which divides the size of
the file with the value returned by FIGETBSZ.

Fix the interface by returning -EINVAL for these filesystems.

Fixes: d1d04ef8572b ("ovl: stack file ops")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2005529af560..0400297c8d72 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -669,6 +669,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 		return ioctl_fiemap(filp, arg);
 
 	case FIGETBSZ:
+		/* anon_bdev filesystems may not have a block size */
+		if (!inode->i_sb->s_blocksize)
+			return -EINVAL;
 		return put_user(inode->i_sb->s_blocksize, argp);
 
 	case FICLONE: