---- 在 星期四, 2021-04-08 19:20:42 Chengguang Xu <cgxu519@xxxxxxxxxxxx> 撰写 ----
> In overlayfs copy-up, if open flag has O_TRUNC then upper
> file will truncate to zero size, in this case we should check
> VM_DENYWRITE mappings to keep compatibility with other filesystems.
>
> Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> ---
> fs/overlayfs/copy_up.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 0fed532efa68..c56c81494b0c 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -901,8 +901,11 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> }
>
> /* maybe truncate regular file. this has no effect on dirs */
> - if (flags & O_TRUNC)
> + if (flags & O_TRUNC) {
> + if (atomic_read(&d_inode(ovl_dentry_real(dentry))->i_writecount) < 0)
> + return -ETXTBSY;
> ctx.stat.size = 0;
> + }
Maybe we should check this for open(with writable flag) not only for truncate case, right?
Thanks,
Chengguang
>
> if (S_ISLNK(ctx.stat.mode)) {
> ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
> --
> 2.27.0
>
>
>
