glibc 2.41 broke dhcpcd

[maravtdm]

After compiling dhcpcd with glibc 2.41
dhcpcd never start, it seems that privsep is broken

# dhcpcd -d -t 15 -L wlan0
dhcpcd-10.1.0 starting
chrooting as dhcpcd to /var/lib/dhcpcd
sandbox: seccomp
spawned manager process on PID 13803
spawned privileged proxy on PID 13804
spawned network proxy on PID 13805
spawned controller proxy on PID 13806
DUID 00:01:00:01:2d:3c:fb:17:a2:fb:c5:dc:b7:b5
wlan0: spawned DHCP6 proxy 2a01:e0a:7a:5c80:8a5b:1da1:6873:bf67 on PID 13809
wlan0: executing: /lib/dhcpcd/dhcpcd-run-hooks PREINIT
wlan0: spawned DHCP6 proxy fe80::b37f:103f:b8e0:ddfc on PID 13810
wlan0: connected to Access Point: XXXXXXXXX
wlan0: executing: /lib/dhcpcd/dhcpcd-run-hooks CARRIER
wlan0: IAID 88:51:f7:11
dhcpcd_fork_cb: dhcpcd manager hungup

[perkelix]

Can you enable debug output (add the debug statement to dhcpcd.conf or use the -d option) and paste the result here?

[maravtdm]

I've already enabled debug mode
see my command => dhcpcd -d -t 15 -L wlan0

[perkelix]

Sorry, I missed that. Still, debug would normally show a LOT more output than what you pasted.

[loqs]

Similar downstream report dhcpcd fails with Bad system call error with glibc 2.41+r2+g0a7c7a3e283a-1. The issue could no longer be produced with seccomp disabled. @maravtdm does # strace -f dhcpcd -d -t 15 -L wlan0 reveal what system call is triggering seccomp?

[loqs]

Backtrace of the issue

(gdb) thread apply all backtrace full

Thread 1 (Thread 0x7cd605559740 (LWP 1347)):
#0  vgetrandom_get_state () at ../sysdeps/unix/sysv/linux/getrandom.c:166
        __futex = 0x7cd604ff8480 <grnd_alloc>
        state = 0x0
        set = {__val = {140725753146060}}
        state = <optimized out>
        set = <optimized out>
        __futex = <optimized out>
        __futex = <optimized out>
        __private = <optimized out>
        __oldval = <optimized out>
#1  getrandom_vdso (buffer=buffer@entry=0x7ffd4486eaa4, length=length@entry=4, flags=flags@entry=0, cancel=cancel@entry=false) at ../sysdeps/unix/sysv/linux/getrandom.c:202
        self = 0x7cd605559740
        state = 0x0
        r = false
        out = <optimized out>
        ret = <optimized out>
#2  0x00007cd604e4f9fb in __getrandom_nocancel (buffer=buffer@entry=0x7ffd4486eaa4, length=length@entry=4, flags=flags@entry=0) at ../sysdeps/unix/sysv/linux/getrandom.c:341
No locals.
#3  0x00007cd604e4cde1 in __GI___arc4random_buf (p=p@entry=0x7ffd4486eaa4, n=n@entry=4) at arc4random.c:45
        __result = <optimized out>
        l = <optimized out>
        fd = <optimized out>
        seen_initialized = 0
#4  0x00007cd604e4cff7 in __GI___arc4random_buf (p=<optimized out>, n=<optimized out>) at arc4random.c:96
        l = <optimized out>
        fd = <optimized out>
        seen_initialized = 0
        l = <optimized out>
        fd = <optimized out>
        __result = <optimized out>
        pfd = <optimized out>
        __result = <optimized out>
        __result = <optimized out>
        __result = <optimized out>
        __result = <optimized out>
#5  __GI___arc4random () at arc4random.c:98
        r = 32765
#6  0x00007cd604e4d064 in __GI___arc4random_uniform (n=2000) at arc4random_uniform.c:52
        value = <optimized out>
        r = <optimized out>
        z = 21
        mask = 2047
        bits = 11
#7  __GI___arc4random_uniform (n=2000) at arc4random_uniform.c:34
        z = <optimized out>
        mask = <optimized out>
        bits = <optimized out>
        value = <optimized out>
        r = <optimized out>
--Type <RET> for more, q to quit, c to continue without paging--
        bits_left = <optimized out>
#8  0x00005d590fe709b5 in dhcp_start ()
No symbol table info available.
#9  0x00005d590fe49a1a in eloop_start ()
No symbol table info available.
#10 0x00005d590fe46c03 in main ()
No symbol table info available.

Possibly related to linux: Add support for getrandom vDSO as I could not reproduce in linux 6.6.74?

[loqs]

In vgetrandom_get_state internal_signal_block_all calls internal_signal_block_all which calls rt_sigprocmask which is blocked by seccomp producing (on a build with ' SECCOMP_FILTER_DEBUG' defined):

dhcpcd[1906]: ps_seccomp_violation: unexpected syscall 14 (arch=0xc000003e)

Where syscall 14 on x86_64 is rt_sigprocmask

Edit:

Fixed in e9e4040 which is not yet part of any release.

[perkelix]

@rsmarples yet another reason to wrap things up and produce a release ASAP. The fix for this bug has been sitting in Git for a long time. Hopefully, you have received your new network card and will soon be ready to roll. :)

[rsmarples]

@rsmarples yet another reason to wrap things up and produce a release ASAP. The fix for this bug has been sitting in Git for a long time. Hopefully, you have received your new network card and will soon be ready to roll. :)

Yes, I have a new wireless card in my dev box now and finally have reliable speeds > 1Mbps