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;
+ }
if (S_ISLNK(ctx.stat.mode)) {
ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
--
2.27.0
