fs: nfs: misused copy_to_user() return value

copy_to_user() returns nonzero value on error, this value may be any value between 0 and requested count, not only requested count.

Signed-off-by Kulikov Vasiliy <[email protected]>

---
 fs/nfs/idmap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

fs/nfs/idmap.c +0 -0

index 21a84d4..a9f2cd5 100644

Quoted 15 lines · Kulikov Vasiliy

copy_to_user() returns nonzero value on error, this value may be any value between 0 and requested count, not only requested count.

Signed-off-by Kulikov Vasiliy <[email protected]>

---
 fs/nfs/idmap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

fs/nfs/idmap.c +0 -0

index 21a84d4..a9f2cd5 100644
@@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
 	unsigned long left;
 

fs/nfs/idmap.c idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg, · line 368

Quoted 6 lines

fs/nfs/idmap.c +1 -1

 	left = copy_to_user(dst, data, mlen);
-	if (left = mlen) {
+	if (left)
 		msg->errno = -EFAULT;
 		return -EFAULT;
 	}

...and we do handle the case where copy_to_user returns less than the requested number of bytes: it is called a 'short read' and is quite allowed in POSIX. The userland application can just call sys_read() again...

Trond