Subject: Re: [PATCH v2] powernv/opal-prd: Silence memcpy() run-time false positive warnings

From: matoro <[email-masked]>
Date: Wed, 15 Nov 2023 14:07:26 -0500

On 2023-08-15 06:47, Michael Ellerman wrote:
> Joel Stanley <[email-masked]> writes:
>> On Fri, 7 Jul 2023 at 05:11, Mahesh Salgaonkar <[email-masked]> 
>> wrote:
>>> 
>>> opal_prd_msg_notifier extracts the opal prd message size from the message
>>> header and uses it for allocating opal_prd_msg_queue_item that includes
>>> the correct message size to be copied. However, while running under
>>> CONFIG_FORTIFY_SOURCE=y, it triggers following run-time warning:
>>> 
>>> [ 6458.234352] memcpy: detected field-spanning write (size 32) of single 
>>> field "&item->msg" at arch/powerpc/platforms/powernv/opal-prd.c:355 (size 
>>> 4)
>>> [ 6458.234390] WARNING: CPU: 9 PID: 660 at 
>>> arch/powerpc/platforms/powernv/opal-prd.c:355 
>>> opal_prd_msg_notifier+0x174/0x188 [opal_prd]
>>> [...]
>>> [ 6458.234709] NIP [c00800000e0c0e6c] opal_prd_msg_notifier+0x174/0x188 
>>> [opal_prd]
>>> [ 6458.234723] LR [c00800000e0c0e68] opal_prd_msg_notifier+0x170/0x188 
>>> [opal_prd]
>>> [ 6458.234736] Call Trace:
>>> [ 6458.234742] [c0000002acb23c10] [c00800000e0c0e68] 
>>> opal_prd_msg_notifier+0x170/0x188 [opal_prd] (unreliable)
>>> [ 6458.234759] [c0000002acb23ca0] [c00000000019ccc0] 
>>> notifier_call_chain+0xc0/0x1b0
>>> [ 6458.234774] [c0000002acb23d00] [c00000000019ceac] 
>>> atomic_notifier_call_chain+0x2c/0x40
>>> [ 6458.234788] [c0000002acb23d20] [c0000000000d69b4] 
>>> opal_message_notify+0xf4/0x2c0
>>> [...]
>>> 
>>> Split the copy to avoid false positive run-time warning.
>>> 
>>> Reported-by: Aneesh Kumar K.V <[email-masked]>
>>> Signed-off-by: Mahesh Salgaonkar <[email-masked]>
>> 
>> I hit this on a box running the Ubuntu 6.2.0-27-generic kernel.
>> 
>> Do we plan on merging this fix?
> 
> I thought it was papering over the issue rather than fixing the root
> cause.
> 
> I'll send a new version, as soon as I can work out how to trigger that
> code path.
> 
> cheers

Hi, I see this was still not accepted.  I was able to trigger this simply by 
starting the opal-prd userspace daemon.
Restarting the service does not re-trigger the warning, however.

[Wed Nov 15 14:01:06 2023] i2c_dev: i2c /dev entries driver
[Wed Nov 15 14:01:07 2023] ------------[ cut here ]------------
[Wed Nov 15 14:01:07 2023] memcpy: detected field-spanning write (size 32) of 
single field "&item->msg" at arch/powerpc/platforms/powernv/opal-prd.c:355 
(size 4)
[Wed Nov 15 14:01:07 2023] WARNING: CPU: 5 PID: 379 at 
arch/powerpc/platforms/powernv/opal-prd.c:355 0xc008000000640b1c
[Wed Nov 15 14:01:07 2023] Modules linked in: i2c_dev loop vhost_net vhost 
vhost_iotlb tap kvm_hv kvm bridge rpcsec_gss_krb5 auth_rpcgss tun nfsv4 
dns_resolver nfs lockd grace sunrpc fscache netfs cfg80211 rfkill 8021q garp 
mrp stp llc nft_masq nft_chain_nat nft_reject_inet nf_reject_ipv4 
nf_reject_ipv6 nft_reject nft_ct binfmt_misc nbd wireguard 
libcurve25519_generic ip6_udp_tunnel udp_tunnel nft_nat nf_tables nfnetlink 
nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 at24 ast i2c_algo_bit 
drm_shmem_helper joydev ftdi_sio crct10dif_vpmsum onboard_usb_hub ofpart 
drm_kms_helper ipmi_powernv rtc_opal ipmi_devintf powernv_flash 
ipmi_msghandler mtd opal_prd i2c_opal vmx_crypto nvme crc32c_vpmsum tg3 
nvme_core ixgbe nvme_common mdio
[Wed Nov 15 14:01:07 2023] CPU: 5 PID: 379 Comm: kopald Not tainted 
6.5.9-gentoo-dist #1
[Wed Nov 15 14:01:07 2023] Hardware name: T2P9S01 REV 1.01 POWER9 0x4e1203 
opal:skiboot-9858186 PowerNV
[Wed Nov 15 14:01:07 2023] NIP:  c008000000640b1c LR: c008000000640b18 CTR: 
0000000000000000
[Wed Nov 15 14:01:07 2023] REGS: c00000000e2339b0 TRAP: 0700   Not tainted  
(6.5.9-gentoo-dist)
[Wed Nov 15 14:01:07 2023] MSR:  9000000000021033 <SF,HV,ME,IR,DR,RI,LE>  CR: 
44002222  XER: 00000000
[Wed Nov 15 14:01:07 2023] CFAR: c000000000152b10 IRQMASK: 1
                            GPR00: c008000000640b18 c00000000e233c50 
c008000000668100 0000000000000086
                            GPR04: 00000000ffff7fff c00000000e233a10 
c00000000e233a08 0000001ef74d0000
                            GPR08: 0000000000000027 c000001ef9626d10 
0000000000000001 0000000044002222
                            GPR12: 20646c6569662065 c000001fff7fb400 
c0000000001900e8 c00000000e919540
                            GPR16: 0000000000000000 0000000000000000 
0000000000000000 0000000000000000
                            GPR20: 0000000000000000 0000000000000000 
0000000000000000 0000000000000000
                            GPR24: c00000000e959de0 0000000000000006 
0000000000000000 c008000000660290
                            GPR28: c000000007498410 0000000000000020 
c00000000e959de8 c000000007498400
[Wed Nov 15 14:01:07 2023] NIP [c008000000640b1c] 0xc008000000640b1c
[Wed Nov 15 14:01:07 2023] LR [c008000000640b18] 0xc008000000640b18
[Wed Nov 15 14:01:07 2023] Call Trace:
[Wed Nov 15 14:01:07 2023] [c00000000e233c50] [c008000000640b18] 
0xc008000000640b18 (unreliable)
[Wed Nov 15 14:01:07 2023] [c00000000e233cd0] [c000000000192dd0] 
notifier_call_chain+0xc0/0x1b0
[Wed Nov 15 14:01:07 2023] [c00000000e233d30] [c000000000192eec] 
atomic_notifier_call_chain+0x2c/0x40
[Wed Nov 15 14:01:07 2023] [c00000000e233d50] [c0000000000cec44] 
opal_message_notify+0xf4/0x2a0
[Wed Nov 15 14:01:07 2023] [c00000000e233de0] [c000000000206d58] 
__handle_irq_event_percpu+0x78/0x240
[Wed Nov 15 14:01:07 2023] [c00000000e233e70] [c000000000207034] 
handle_irq_event+0x74/0x140
[Wed Nov 15 14:01:07 2023] [c00000000e233ea0] [c00000000020e9bc] 
handle_level_irq+0xdc/0x270
[Wed Nov 15 14:01:07 2023] [c00000000e233ed0] [c000000000204fb8] 
generic_handle_domain_irq+0x48/0x70
[Wed Nov 15 14:01:07 2023] [c00000000e233ef0] [c0000000000d6f38] 
opal_handle_events+0xb8/0x140
[Wed Nov 15 14:01:07 2023] [c00000000e233f50] [c0000000000ce514] 
kopald+0x84/0x110
[Wed Nov 15 14:01:07 2023] [c00000000e233f90] [c000000000190218] 
kthread+0x138/0x140
[Wed Nov 15 14:01:07 2023] [c00000000e233fe0] [c00000000000ded8] 
start_kernel_thread+0x14/0x18
[Wed Nov 15 14:01:07 2023] Code: 2c0a0000 4082ff48 3ca20000 e8a58050 3c620000 
e8638058 39400001 38c00004 7fa4eb78 99490000 480004c5 e8410018 <0fe00000> 
4bffff18 3860fff4 4bffff8c
[Wed Nov 15 14:01:07 2023] ---[ end trace 0000000000000000 ]---