[BUG] ipv6: possible null-pointer dereference in ip6_xmit()

[Tuo Li]

Hello,

Our static analysis tool finds a possible null-pointer dereference in 
ip6_output.c in Linux 5.14.0-rc3:

The variable n is checked in:
314:    if (np)

This indicates that it can be NULL. If so, a null-pointer dereference 
will occur
in the called function ip6_autoflowlabel() at Line 320:
252:    if (!np->autoflowlabel_set)

I am not quite sure whether this possible null-pointer dereference is 
real and how to fix it if it is real.
Any feedback would be appreciated, thanks!

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>

Best wishes,
Tuo Li