zstd -t modifies /dev/null file mode bits #851
Description
If I run "zstd -t" as root on a Linux system, zstd modifies file mode bits of /dev/null:
# ls -la /dev/null
crw-rw-rw- 1 root root 1, 3 Sep 18 13:12 /dev/null
# zstd -t linux.tgz
linux.tgz : 27002880 bytes
# ls -la /dev/null
crw-r----- 1 root root 1, 3 Sep 18 13:12 /dev/null
A strace shows:
# strace -o trace.txt -f zstd -t linux.tgz
linux.tgz : 27002880 bytes
# grep "/dev/null" trace.txt
20269 open("/dev/null", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
20269 utime("/dev/null", {actime=2017-09-18T13:50:14+0200, modtime=2017-09-18T13:12:41+0200}) = 0
20269 chown("/dev/null", 0, 0) = 0
20269 chmod("/dev/null", 0640) = 0
I see this bug with version 1.3.0 and version 1.3.1. I didn't test earlier versions.