vfs: fix FIGETBSZ ioctl on an overlayfs file

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>

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2005529..0400297 100644 (file)
--- 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: