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Subject[PATCH 4.14 261/496] net/sched: fix NULL dereference in the error path of tcf_sample_init()
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davide Caratti <dcaratti@redhat.com>

[ Upstream commit 1f110e7cae09e6c6a144616480d1a9dd99c5208a ]

when the following command

# tc action add action sample rate 100 group 100 index 100

is run for the first time, and psample_group_get(100) fails to create a
new group, tcf_sample_cleanup() calls psample_group_put(NULL), thus
causing the following error:

BUG: unable to handle kernel NULL pointer dereference at 000000000000001c
IP: psample_group_put+0x15/0x71 [psample]
PGD 8000000075775067 P4D 8000000075775067 PUD 7453c067 PMD 0
Oops: 0002 [#1] SMP PTI
Modules linked in: act_sample(E) psample ip6table_filter ip6_tables iptable_filter binfmt_misc ext4 snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hda_core mbcache jbd2 crct10dif_pclmul snd_hwdep crc32_pclmul snd_seq ghash_clmulni_intel pcbc snd_seq_device snd_pcm aesni_intel crypto_simd snd_timer glue_helper snd cryptd joydev pcspkr i2c_piix4 soundcore virtio_balloon nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c ata_generic pata_acpi qxl drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm virtio_net ata_piix virtio_console virtio_blk libata serio_raw crc32c_intel virtio_pci i2c_core virtio_ring virtio floppy dm_mirror dm_region_hash dm_log dm_mod [last unloaded: act_tunnel_key]
CPU: 2 PID: 5740 Comm: tc Tainted: G E 4.16.0-rc4.act_vlan.orig+ #403
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
RIP: 0010:psample_group_put+0x15/0x71 [psample]
RSP: 0018:ffffb8a80032f7d0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000024
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffffc06d93c0
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000044
R10: 00000000bd003000 R11: ffff979fba04aa59 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff979fbba3f22c
FS: 00007f7638112740(0000) GS:ffff979fbfd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000001c CR3: 00000000734ea001 CR4: 00000000001606e0
Call Trace:
__tcf_idr_release+0x79/0xf0
tcf_sample_init+0x125/0x1d0 [act_sample]
tcf_action_init_1+0x2cc/0x430
tcf_action_init+0xd3/0x1b0
tc_ctl_action+0x18b/0x240
rtnetlink_rcv_msg+0x29c/0x310
? _cond_resched+0x15/0x30
? __kmalloc_node_track_caller+0x1b9/0x270
? rtnl_calcit.isra.28+0x100/0x100
netlink_rcv_skb+0xd2/0x110
netlink_unicast+0x17c/0x230
netlink_sendmsg+0x2cd/0x3c0
sock_sendmsg+0x30/0x40
___sys_sendmsg+0x27a/0x290
? filemap_map_pages+0x34a/0x3a0
? __handle_mm_fault+0xbfd/0xe20
__sys_sendmsg+0x51/0x90
do_syscall_64+0x6e/0x1a0
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x7f7637523ba0
RSP: 002b:00007fff0473ef58 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fff0473f080 RCX: 00007f7637523ba0
RDX: 0000000000000000 RSI: 00007fff0473efd0 RDI: 0000000000000003
RBP: 000000005aaaac80 R08: 0000000000000002 R09: 0000000000000000
R10: 00007fff0473e9e0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff0473f094 R14: 0000000000000001 R15: 0000000000669f60
Code: be 02 00 00 00 48 89 df e8 a9 fe ff ff e9 7c ff ff ff 0f 1f 40 00 0f 1f 44 00 00 53 48 89 fb 48 c7 c7 c0 93 6d c0 e8 db 20 8c ef <83> 6b 1c 01 74 10 48 c7 c7 c0 93 6d c0 ff 14 25 e8 83 83 b0 5b
RIP: psample_group_put+0x15/0x71 [psample] RSP: ffffb8a80032f7d0
CR2: 000000000000001c

Fix it in tcf_sample_cleanup(), ensuring that calls to psample_group_put(p)
are done only when p is not NULL.

Fixes: cadb9c9fdbc6 ("net/sched: act_sample: Fix error path in init")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/act_sample.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sched/act_sample.c
+++ b/net/sched/act_sample.c
@@ -103,7 +103,8 @@ static void tcf_sample_cleanup_rcu(struc

psample_group = rcu_dereference_protected(s->psample_group, 1);
RCU_INIT_POINTER(s->psample_group, NULL);
- psample_group_put(psample_group);
+ if (psample_group)
+ psample_group_put(psample_group);
}

static void tcf_sample_cleanup(struct tc_action *a, int bind)

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