4.14-stable review patch. If anyone has any objections, please let me know.
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From: Toshiaki Makita makita.toshiaki@lab.ntt.co.jp
[ Upstream commit 6547e387d7f52f2ba681a229de3c13e5b9e01ee1 ]
Calling XDP redirection requires bh disabled. Softirq can call another XDP function and redirection functions, then the percpu static variable ri->map can be overwritten to NULL.
This is a generic XDP case called from tun.
[ 3535.736058] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 3535.743974] PGD 0 P4D 0 [ 3535.746530] Oops: 0000 [#1] SMP PTI [ 3535.750049] Modules linked in: vhost_net vhost tap tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter sunrpc vfat fat ext4 mbcache jbd2 intel_rapl skx_edac nfit libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm ipmi_ssif irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc ses aesni_intel crypto_simd cryptd enclosure hpwdt hpilo glue_helper ipmi_si pcspkr wmi mei_me ioatdma mei ipmi_devintf shpchp dca ipmi_msghandler lpc_ich acpi_power_meter sch_fq_codel ip_tables xfs libcrc32c sd_mod mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm smartpqi i40e crc32c_intel scsi_transport_sas tg3 i2c_core ptp pps_core [ 3535.813456] CPU: 5 PID: 1630 Comm: vhost-1614 Not tainted 4.17.0-rc4 #2 [ 3535.820127] Hardware name: HPE ProLiant DL360 Gen10/ProLiant DL360 Gen10, BIOS U32 11/14/2017 [ 3535.828732] RIP: 0010:__xdp_map_lookup_elem+0x5/0x30 [ 3535.833740] RSP: 0018:ffffb4bc47bf7c58 EFLAGS: 00010246 [ 3535.839009] RAX: ffff9fdfcfea1c40 RBX: 0000000000000000 RCX: ffff9fdf27fe3100 [ 3535.846205] RDX: ffff9fdfca769200 RSI: 0000000000000000 RDI: 0000000000000000 [ 3535.853402] RBP: ffffb4bc491d9000 R08: 00000000000045ad R09: 0000000000000ec0 [ 3535.860597] R10: 0000000000000001 R11: ffff9fdf26c3ce4e R12: ffff9fdf9e72c000 [ 3535.867794] R13: 0000000000000000 R14: fffffffffffffff2 R15: ffff9fdfc82cdd00 [ 3535.874990] FS: 0000000000000000(0000) GS:ffff9fdfcfe80000(0000) knlGS:0000000000000000 [ 3535.883152] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3535.888948] CR2: 0000000000000018 CR3: 0000000bde724004 CR4: 00000000007626e0 [ 3535.896145] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 3535.903342] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 3535.910538] PKRU: 55555554 [ 3535.913267] Call Trace: [ 3535.915736] xdp_do_generic_redirect+0x7a/0x310 [ 3535.920310] do_xdp_generic.part.117+0x285/0x370 [ 3535.924970] tun_get_user+0x5b9/0x1260 [tun] [ 3535.929279] tun_sendmsg+0x52/0x70 [tun] [ 3535.933237] handle_tx+0x2ad/0x5f0 [vhost_net] [ 3535.937721] vhost_worker+0xa5/0x100 [vhost] [ 3535.942030] kthread+0xf5/0x130 [ 3535.945198] ? vhost_dev_ioctl+0x3b0/0x3b0 [vhost] [ 3535.950031] ? kthread_bind+0x10/0x10 [ 3535.953727] ret_from_fork+0x35/0x40 [ 3535.957334] Code: 0e 74 15 83 f8 10 75 05 e9 49 aa b3 ff f3 c3 0f 1f 80 00 00 00 00 f3 c3 e9 29 9d b3 ff 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <8b> 47 18 83 f8 0e 74 0d 83 f8 10 75 05 e9 49 a9 b3 ff 31 c0 c3 [ 3535.976387] RIP: __xdp_map_lookup_elem+0x5/0x30 RSP: ffffb4bc47bf7c58 [ 3535.982883] CR2: 0000000000000018 [ 3535.987096] ---[ end trace 383b299dd1430240 ]--- [ 3536.131325] Kernel panic - not syncing: Fatal exception [ 3536.137484] Kernel Offset: 0x26a00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 3536.281406] ---[ end Kernel panic - not syncing: Fatal exception ]---
And a kernel with generic case fixed still panics in tun driver XDP redirect, because it disabled only preemption, but not bh.
[ 2055.128746] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 2055.136662] PGD 0 P4D 0 [ 2055.139219] Oops: 0000 [#1] SMP PTI [ 2055.142736] Modules linked in: vhost_net vhost tap tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter sunrpc vfat fat ext4 mbcache jbd2 intel_rapl skx_edac nfit libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc ses aesni_intel ipmi_ssif crypto_simd enclosure cryptd hpwdt glue_helper ioatdma hpilo wmi dca pcspkr ipmi_si acpi_power_meter ipmi_devintf shpchp mei_me ipmi_msghandler mei lpc_ich sch_fq_codel ip_tables xfs libcrc32c sd_mod mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm i40e smartpqi tg3 scsi_transport_sas crc32c_intel i2c_core ptp pps_core [ 2055.206142] CPU: 6 PID: 1693 Comm: vhost-1683 Tainted: G W 4.17.0-rc5-fix-tun+ #1 [ 2055.215011] Hardware name: HPE ProLiant DL360 Gen10/ProLiant DL360 Gen10, BIOS U32 11/14/2017 [ 2055.223617] RIP: 0010:__xdp_map_lookup_elem+0x5/0x30 [ 2055.228624] RSP: 0018:ffff998b07607cc0 EFLAGS: 00010246 [ 2055.233892] RAX: ffff8dbd8e235700 RBX: ffff8dbd8ff21c40 RCX: 0000000000000004 [ 2055.241089] RDX: ffff998b097a9000 RSI: 0000000000000000 RDI: 0000000000000000 [ 2055.248286] RBP: 0000000000000000 R08: 00000000000065a8 R09: 0000000000005d80 [ 2055.255483] R10: 0000000000000040 R11: ffff8dbcf0100000 R12: ffff998b097a9000 [ 2055.262681] R13: ffff8dbd8c98c000 R14: 0000000000000000 R15: ffff998b07607d78 [ 2055.269879] FS: 0000000000000000(0000) GS:ffff8dbd8ff00000(0000) knlGS:0000000000000000 [ 2055.278039] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2055.283834] CR2: 0000000000000018 CR3: 0000000c0c8cc005 CR4: 00000000007626e0 [ 2055.291030] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 2055.298227] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 2055.305424] PKRU: 55555554 [ 2055.308153] Call Trace: [ 2055.310624] xdp_do_redirect+0x7b/0x380 [ 2055.314499] tun_get_user+0x10fe/0x12a0 [tun] [ 2055.318895] tun_sendmsg+0x52/0x70 [tun] [ 2055.322852] handle_tx+0x2ad/0x5f0 [vhost_net] [ 2055.327337] vhost_worker+0xa5/0x100 [vhost] [ 2055.331646] kthread+0xf5/0x130 [ 2055.334813] ? vhost_dev_ioctl+0x3b0/0x3b0 [vhost] [ 2055.339646] ? kthread_bind+0x10/0x10 [ 2055.343343] ret_from_fork+0x35/0x40 [ 2055.346950] Code: 0e 74 15 83 f8 10 75 05 e9 e9 aa b3 ff f3 c3 0f 1f 80 00 00 00 00 f3 c3 e9 c9 9d b3 ff 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <8b> 47 18 83 f8 0e 74 0d 83 f8 10 75 05 e9 e9 a9 b3 ff 31 c0 c3 [ 2055.366004] RIP: __xdp_map_lookup_elem+0x5/0x30 RSP: ffff998b07607cc0 [ 2055.372500] CR2: 0000000000000018 [ 2055.375856] ---[ end trace 2a2dcc5e9e174268 ]--- [ 2055.523626] Kernel panic - not syncing: Fatal exception [ 2055.529796] Kernel Offset: 0x2e000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 2055.677539] ---[ end Kernel panic - not syncing: Fatal exception ]---
v2: - Removed preempt_disable/enable since local_bh_disable will prevent preemption as well, feedback from Jason Wang.
Fixes: 761876c857cb ("tap: XDP support") Signed-off-by: Toshiaki Makita makita.toshiaki@lab.ntt.co.jp Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/tun.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1315,7 +1315,7 @@ static struct sk_buff *tun_build_skb(str else *skb_xdp = 0;
- preempt_disable(); + local_bh_disable(); rcu_read_lock(); xdp_prog = rcu_dereference(tun->xdp_prog); if (xdp_prog && !*skb_xdp) { @@ -1338,7 +1338,7 @@ static struct sk_buff *tun_build_skb(str if (err) goto err_redirect; rcu_read_unlock(); - preempt_enable(); + local_bh_enable(); return NULL; case XDP_TX: xdp_xmit = true; @@ -1360,7 +1360,7 @@ static struct sk_buff *tun_build_skb(str skb = build_skb(buf, buflen); if (!skb) { rcu_read_unlock(); - preempt_enable(); + local_bh_enable(); return ERR_PTR(-ENOMEM); }
@@ -1373,12 +1373,12 @@ static struct sk_buff *tun_build_skb(str skb->dev = tun->dev; generic_xdp_tx(skb, xdp_prog); rcu_read_unlock(); - preempt_enable(); + local_bh_enable(); return NULL; }
rcu_read_unlock(); - preempt_enable(); + local_bh_enable();
return skb;
@@ -1386,7 +1386,7 @@ err_redirect: put_page(alloc_frag->page); err_xdp: rcu_read_unlock(); - preempt_enable(); + local_bh_enable(); this_cpu_inc(tun->pcpu_stats->rx_dropped); return NULL; } @@ -1556,16 +1556,19 @@ static ssize_t tun_get_user(struct tun_s struct bpf_prog *xdp_prog; int ret;
+ local_bh_disable(); rcu_read_lock(); xdp_prog = rcu_dereference(tun->xdp_prog); if (xdp_prog) { ret = do_xdp_generic(xdp_prog, skb); if (ret != XDP_PASS) { rcu_read_unlock(); + local_bh_enable(); return total_len; } } rcu_read_unlock(); + local_bh_enable(); }
rxhash = __skb_get_hash_symmetric(skb);