Re: [mainline]Kernel Warnings at kernel/bpf/syscall.c:3374

[Andrii Nakryiko]

On Wed, Apr 9, 2025 at 9:51 PM Venkat Rao Bagalkote
<venkat88@xxxxxxxxxxxxx> wrote:
>
> + LKML, netdev
>
> On 10/04/25 10:17 am, Venkat Rao Bagalkote wrote:
> > Hello!!
> >
> >
> > I am observing below kernel warnings on IBM Power9 server, while
> > running bpf selftest on mainline kernel.
> >
> > This issue never seen before good commit[1], and seen intermetently
> > after bad commit[2], and this is not reproducible everytime.
> >
> > So likely issue got introduced b/w these two commits.
> >
> > [1]GoodCommit: 7f2ff7b6261742ed52aa973ccdf99151b7cc3a50
> > [2]Bad Commit: 08733088b566b58283f0f12fb73f5db6a9a9de30
> >
> >
> > Traces:
> >
> >
> > [34208.591723] ------------[ cut here ]------------
> > [34208.591738] WARNING: CPU: 9 PID: 375502 at
> > kernel/bpf/syscall.c:3374 bpf_tracing_link_release+0x90/0xa0

This seems to be due to an error returned from
bpf_trampoline_unlink_prog(), which can happen for a multitude of
reasons. If you can reproduce this reasonably easily, it would be nice
if you can help understand where exactly it's coming from. You could
try using retsnoop ([0]) for this. Or bpftrace, if you can't use
retsnoop for some reason.

  [0] https://github.com/anakryiko/retsnoop

> > [34208.591750] Modules linked in: bpf_testmod(OE) 8021q(E) garp(E)
> > mrp(E) vrf(E) tun(E) rpadlpar_io(E) rpaphp(E) vfat(E) fat(E) isofs(E)
> > ext4(E) crc16(E) mbcache(E) jbd2(E) nft_masq(E) veth(E) bridge(E)
> > stp(E) llc(E) overlay(E) bonding(E) nft_fib_inet(E) nft_fib_ipv4(E)
> > nft_fib_ipv6(E) nft_fib(E) nft_reject_inet(E) nf_reject_ipv4(E)
> > nf_reject_ipv6(E) nft_reject(E) nft_ct(E) nft_chain_nat(E) rfkill(E)
> > ip_set(E) mlx5_ib(E) ib_uverbs(E) ib_core(E) mlx5_core(E) mlxfw(E)
> > psample(E) tls(E) ibmveth(E) pseries_rng(E) sg(E) vmx_crypto(E) drm(E)
> > fuse(E) dm_mod(E) drm_panel_orientation_quirks(E) xfs(E) lpfc(E)
> > nvmet_fc(E) nvmet(E) sr_mod(E) sd_mod(E) cdrom(E) nvme_fc(E)
> > nvme_fabrics(E) ibmvscsi(E) nvme_core(E) scsi_transport_srp(E)
> > scsi_transport_fc(E) [last unloaded: bpf_test_modorder_x(OE)]
> > [34208.591838] CPU: 9 UID: 0 PID: 375502 Comm: test_progs-no_a
> > Tainted: G        W  OE       6.15.0-rc1-ga24588245776 #1 VOLUNTARY
> > [34208.591848] Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
> > [34208.591852] Hardware name: IBM,8375-42A POWER9 (architected)
> > 0x4e0202 0xf000005 of:IBM,FW950.80 (VL950_131) hv:phyp pSeries
> > [34208.591857] NIP:  c00000000049c830 LR: c00000000049c7cc CTR:
> > 0000000000000070
> > [34208.591863] REGS: c00000000eb07a60 TRAP: 0700   Tainted: G
> > W  OE        (6.15.0-rc1-ga24588245776)
> > [34208.591869] MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR:
> > 84002482  XER: 00000000
> > [34208.591882] CFAR: c00000000049c7d4 IRQMASK: 0
> > [34208.591882] GPR00: c00000000049c7cc c00000000eb07d00
> > c000000001da8100 fffffffffffffff2
> > [34208.591882] GPR04: 0000000000014ed8 c00000103965d480
> > c0000003415ca800 c0000000b247c900
> > [34208.591882] GPR08: 0000000000000000 0000000000000000
> > c0000000b247c900 0000000000002000
> > [34208.591882] GPR12: c00000000eb078a8 c000000017ff5300
> > 0000000000000000 0000000000000000
> > [34208.591882] GPR16: 0000000000000000 0000000000000000
> > 0000000000000000 0000000000000000
> > [34208.591882] GPR20: 0000000000000000 0000000000000000
> > 0000000000000000 0000000000000000
> > [34208.591882] GPR24: 0000000000000000 0000000000000000
> > 0000000000000000 c0000003893d6780
> > [34208.591882] GPR28: c00000000369a6a0 0000000000000fa4
> > c00000000135d988 c0000000c224bf00
> > [34208.591945] NIP [c00000000049c830] bpf_tracing_link_release+0x90/0xa0
> > [34208.591953] LR [c00000000049c7cc] bpf_tracing_link_release+0x2c/0xa0
> > [34208.591960] Call Trace:
> > [34208.591963] [c00000000eb07d00] [c00000000049c7cc]
> > bpf_tracing_link_release+0x2c/0xa0 (unreliable)
> > [34208.591973] [c00000000eb07d30] [c00000000049c614]
> > bpf_link_free+0x94/0x160
> > [34208.591981] [c00000000eb07d70] [c00000000049c780]
> > bpf_link_release+0x50/0x70
> > [34208.591989] [c00000000eb07d90] [c0000000006ee75c] __fput+0x11c/0x3c0
> > [34208.591997] [c00000000eb07de0] [c0000000006e46bc] sys_close+0x4c/0xa0
> > [34208.592003] [c00000000eb07e10] [c0000000000325a4]
> > system_call_exception+0x114/0x300
> > [34208.592012] [c00000000eb07e50] [c00000000000d05c]
> > system_call_vectored_common+0x15c/0x2ec
> > [34208.592020] --- interrupt: 3000 at 0x7fff9c40d8a4
> > [34208.592030] NIP:  00007fff9c40d8a4 LR: 00007fff9c40d8a4 CTR:
> > 0000000000000000
> > [34208.592035] REGS: c00000000eb07e80 TRAP: 3000   Tainted: G
> > W  OE        (6.15.0-rc1-ga24588245776)
> > [34208.592041] MSR:  800000000280f033
> > <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 48002886  XER: 00000000
> > [34208.592057] IRQMASK: 0
> > [34208.592057] GPR00: 0000000000000006 00007fffcce2d650
> > 00007fff9c527100 0000000000000066
> > [34208.592057] GPR04: 0000000000000000 0000000000000007
> > 0000000000000004 00007fff9ce5efc0
> > [34208.592057] GPR08: 00007fff9ce57908 0000000000000000
> > 0000000000000000 0000000000000000
> > [34208.592057] GPR12: 0000000000000000 00007fff9ce5efc0
> > 0000000000000000 0000000000000000
> > [34208.592057] GPR16: 0000000000000000 0000000000000000
> > 0000000000000000 0000000000000000
> > [34208.592057] GPR20: 0000000000000000 0000000000000000
> > 0000000000000000 00007fff9ce4f470
> > [34208.592057] GPR24: 0000000010610b6c 00007fff9ce50000
> > 00007fffcce2e098 0000000000000001
> > [34208.592057] GPR28: 00007fffcce2e250 00007fffcce2e088
> > 0000000000000000 0000000000000066
> > [34208.592118] NIP [00007fff9c40d8a4] 0x7fff9c40d8a4
> > [34208.592122] LR [00007fff9c40d8a4] 0x7fff9c40d8a4
> > [34208.592127] --- interrupt: 3000
> > [34208.592130] Code: 4bfffc28 60000000 60000000 60000000 38210030
> > e8010010 ebe1fff8 7c0803a6 4e800020 60000000 60000000 60000000
> > <0fe00000> 4bffffa4 60000000 60000000
> > [34208.592152] ---[ end trace 0000000000000000 ]---
> >
> >
> > If you happen to fix this issue, please add below tag.
> >
> >
> > Reported-by: Venkat Rao Bagalkote <venkat88@xxxxxxxxxxxxx>
> >
> >
> > Regards,
> >
> > Venkat.
> >
>