CVE-2023-52992

In the Linux kernel, the following vulnerability has been resolved:

bpf: Skip task with pid=1 in sendsignalcommon()

The following kernel panic can be triggered when a task with pid=1 attaches a prog that attempts to send killing signal to itself, also see [1] for more details:

Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b CPU: 3 PID: 1 Comm: systemd Not tainted 6.1.0-09652-g59fe41b5255f #148 Call Trace: <TASK> _dumpstack lib/dumpstack.c:88 [inline] dumpstacklvl+0x100/0x178 lib/dumpstack.c:106 panic+0x2c4/0x60f kernel/panic.c:275 doexit.cold+0x63/0xe4 kernel/exit.c:789 dogroupexit+0xd4/0x2a0 kernel/exit.c:950 getsignal+0x2460/0x2600 kernel/signal.c:2858 archdosignalorrestart+0x78/0x5d0 arch/x86/kernel/signal.c:306 exittousermodeloop kernel/entry/common.c:168 [inline] exittousermodeprepare+0x15f/0x250 kernel/entry/common.c:203 _syscallexittousermodework kernel/entry/common.c:285 [inline] syscallexittousermode+0x1d/0x50 kernel/entry/common.c:296 dosyscall64+0x44/0xb0 arch/x86/entry/common.c:86 entrySYSCALL64afterhwframe+0x63/0xcd

So skip task with pid=1 in bpfsendsignal_common() to avoid the panic.

[1] https://lore.kernel.org/bpf/20221222043507.33037-1-sunhao.th@gmail.com