Issue

Echo command built in busybox writes wrong data after write error like
ENOSPC.

Here is a sample script to reproduce this bug:

echo "abcde" > /dev/full
echo "12345" > ./test.txt

The first echo fails with ENOSPC. By the second echo, "12345" is written to test.txt. Therefore the contents of test.txt should be "12345". But actual result is as follows:

 [root@localhost test]# ls
 run.sh
 [root@localhost test]# cat run.sh
 echo "abcde" > /dev/full
 echo "12345" > ./test.txt
 [root@localhost test]# busybox sh run.sh
 [root@localhost test]# ls
 run.sh  test.txt
 [root@localhost test]# cat test.txt
 abcd12345

The both data "abcde" and "12345" are written to test.txt. Note that this is a problem only for echo command built in shell (ash, msh, and so on), it is not reproduced when echo command is used independently. For example, if you start ash and then run echo command manually, there is no problem.

[root@localhost ~]# busybox ash
# echo "abcde" > /dev/full
abcd#
# echo "12345" > ./test.txt
# cat test.txt
12345
#