> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
> Maciej Fijalkowski
> Sent: Tuesday, October 26, 2021 10:17 PM
> To: intel-wired-lan@xxxxxxxxxxxxxxxx
> Cc: Lobakin, Alexandr <alexandr.lobakin@xxxxxxxxx>;
> netdev@xxxxxxxxxxxxxxx; Plantykow, Marta A
> <marta.a.plantykow@xxxxxxxxx>; kuba@xxxxxxxxxx; bpf@xxxxxxxxxxxxxxx;
> davem@xxxxxxxxxxxxx; Karlsson, Magnus <magnus.karlsson@xxxxxxxxx>
> Subject: [Intel-wired-lan] [PATCH intel-next 2/2] ice: avoid bpf_prog refcount
> underflow
>
> From: Marta Plantykow <marta.a.plantykow@xxxxxxxxx>
>
> Ice driver has the routines for managing XDP resources that are shared
> between ndo_bpf op and VSI rebuild flow. The latter takes place for example
> when user changes queue count on an interface via ethtool's set_channels().
>
> There is an issue around the bpf_prog refcounting when VSI is being rebuilt -
> since ice_prepare_xdp_rings() is called with vsi->xdp_prog as an argument
> that is used later on by ice_vsi_assign_bpf_prog(), same bpf_prog pointers
> are swapped with each other. Then it is also interpreted as an 'old_prog'
> which in turn causes us to call bpf_prog_put on it that will decrement its
> refcount.
>
> Below splat can be interpreted in a way that due to zero refcount of a
> bpf_prog it is wiped out from the system while kernel still tries to refer to it:
>
> [ 481.069429] BUG: unable to handle page fault for address:
> ffffc9000640f038 [ 481.077390] #PF: supervisor read access in kernel mode [
> 481.083335] #PF: error_code(0x0000) - not-present page [ 481.089276] PGD
> 100000067 P4D 100000067 PUD 1001cb067 PMD 106d2b067 PTE 0 [
> 481.097141] Oops: 0000 [#1] PREEMPT SMP PTI
> [ 481.101980] CPU: 12 PID: 3339 Comm: sudo Tainted: G OE 5.15.0-
> rc5+ #1
> [ 481.110840] Hardware name: Intel Corp. GRANTLEY/GRANTLEY, BIOS
> GRRFCRB1.86B.0276.D07.1605190235 05/19/2016 [ 481.122021] RIP:
> 0010:dev_xdp_prog_id+0x25/0x40 [ 481.127265] Code: 80 00 00 00 00 0f 1f
> 44 00 00 89 f6 48 c1 e6 04 48 01 fe 48 8b 86 98 08 00 00 48 85 c0 74 13 48 8b
> 50 18 31 c0 48 85 d2 74 07 <48> 8b 42 38 8b 40 20 c3 48 8b 96 90 08 00 00 eb
> e8 66 2e 0f 1f 84 [ 481.148991] RSP: 0018:ffffc90007b63868 EFLAGS:
> 00010286 [ 481.155034] RAX: 0000000000000000 RBX: ffff889080824000
> RCX: 0000000000000000 [ 481.163278] RDX: ffffc9000640f000 RSI:
> ffff889080824010 RDI: ffff889080824000 [ 481.171527] RBP:
> ffff888107af7d00 R08: 0000000000000000 R09: ffff88810db5f6e0 [
> 481.179776] R10: 0000000000000000 R11: ffff8890885b9988 R12:
> ffff88810db5f4bc [ 481.188026] R13: 0000000000000000 R14:
> 0000000000000000 R15: 0000000000000000 [ 481.196276] FS:
> 00007f5466d5bec0(0000) GS:ffff88903fb00000(0000)
> knlGS:0000000000000000 [ 481.205633] CS: 0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033 [ 481.212279] CR2: ffffc9000640f038 CR3:
> 000000014429c006 CR4: 00000000003706e0 [ 481.220530] DR0:
> 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [
> 481.228771] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400 [ 481.237029] Call Trace:
> [ 481.239856] rtnl_fill_ifinfo+0x768/0x12e0 [ 481.244602]
> rtnl_dump_ifinfo+0x525/0x650 [ 481.249246] ? __alloc_skb+0xa5/0x280 [
> 481.253484] netlink_dump+0x168/0x3c0 [ 481.257725]
> netlink_recvmsg+0x21e/0x3e0 [ 481.262263] ____sys_recvmsg+0x87/0x170
> [ 481.266707] ? __might_fault+0x20/0x30 [ 481.271046] ?
> _copy_from_user+0x66/0xa0 [ 481.275591] ? iovec_from_user+0xf6/0x1c0 [
> 481.280226] ___sys_recvmsg+0x82/0x100 [ 481.284566] ?
> sock_sendmsg+0x5e/0x60 [ 481.288791] ? __sys_sendto+0xee/0x150 [
> 481.293129] __sys_recvmsg+0x56/0xa0 [ 481.297267]
> do_syscall_64+0x3b/0xc0 [ 481.301395]
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 481.307238] RIP: 0033:0x7f5466f39617
> [ 481.311373] Code: 0c 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb bd 0f 1f 00 f3 0f
> 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2f 00 00 00 0f 05 <48> 3d 00 f0 ff
> ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10 [ 481.342944] RSP:
> 002b:00007ffedc7f4308 EFLAGS: 00000246 ORIG_RAX: 000000000000002f [
> 481.361783] RAX: ffffffffffffffda RBX: 00007ffedc7f5460 RCX:
> 00007f5466f39617 [ 481.380278] RDX: 0000000000000000 RSI:
> 00007ffedc7f5360 RDI: 0000000000000003 [ 481.398500] RBP:
> 00007ffedc7f53f0 R08: 0000000000000000 R09: 000055d556f04d50 [
> 481.416463] R10: 0000000000000077 R11: 0000000000000246 R12:
> 00007ffedc7f5360 [ 481.434131] R13: 00007ffedc7f5350 R14:
> 00007ffedc7f5344 R15: 0000000000000e98 [ 481.451520] Modules linked in:
> ice(OE) af_packet binfmt_misc nls_iso8859_1 ipmi_ssif intel_rapl_msr
> intel_rapl_common x86_pkg_temp_thermal intel_powerclamp mxm_wmi
> mei_me coretemp mei ipmi_si ipmi_msghandler wmi acpi_pad
> acpi_power_meter ip_tables x_tables autofs4 crct10dif_pclmul crc32_pclmul
> ghash_clmulni_intel aesni_intel ahci crypto_simd cryptd libahci lpc_ich [last
> unloaded: ice] [ 481.528558] CR2: ffffc9000640f038 [ 481.542041] ---[ end
> trace d1f24c9ecf5b61c1 ]---
>
> Fix this by only calling ice_vsi_assign_bpf_prog() inside
> ice_prepare_xdp_rings() when current vsi->xdp_prog pointer is NULL.
> This way set_channels() flow will not attempt to swap the vsi->xdp_prog
> pointers with itself.
>
> Also, sprinkle around some comments that provide a reasoning about
> correlation between driver and kernel in terms of bpf_prog refcount.
>
> Fixes: efc2214b6047 ("ice: Add support for XDP")
> Reviewed-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx>
> Signed-off-by: Marta Plantykow <marta.a.plantykow@xxxxxxxxx> [ Maciej:
> don't assign the prog if already present, expand commit
> message ]
> Co-developed-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
> ---
> drivers/net/ethernet/intel/ice/ice_main.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
Tested-by: Kiran Bhandare <kiranx.bhandare@xxxxxxxxx> A Contingent Worker at Intel
