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vlan: Fix reading memory beyond skb->tail in skb_vlan_tagged_multi
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[ Upstream commit 7ce2367 ]

Syzkaller spotted an old bug which leads to reading skb beyond tail by 4
bytes on vlan tagged packets.
This is caused because skb_vlan_tagged_multi() did not check
skb_headlen.

BUG: KMSAN: uninit-value in eth_type_vlan include/linux/if_vlan.h:283 [inline]
BUG: KMSAN: uninit-value in skb_vlan_tagged_multi include/linux/if_vlan.h:656 [inline]
BUG: KMSAN: uninit-value in vlan_features_check include/linux/if_vlan.h:672 [inline]
BUG: KMSAN: uninit-value in dflt_features_check net/core/dev.c:2949 [inline]
BUG: KMSAN: uninit-value in netif_skb_features+0xd1b/0xdc0 net/core/dev.c:3009
CPU: 1 PID: 3582 Comm: syzkaller435149 Not tainted 4.16.0+ #82
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
  eth_type_vlan include/linux/if_vlan.h:283 [inline]
  skb_vlan_tagged_multi include/linux/if_vlan.h:656 [inline]
  vlan_features_check include/linux/if_vlan.h:672 [inline]
  dflt_features_check net/core/dev.c:2949 [inline]
  netif_skb_features+0xd1b/0xdc0 net/core/dev.c:3009
  validate_xmit_skb+0x89/0x1320 net/core/dev.c:3084
  __dev_queue_xmit+0x1cb2/0x2b60 net/core/dev.c:3549
  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
  packet_snd net/packet/af_packet.c:2944 [inline]
  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg net/socket.c:640 [inline]
  sock_write_iter+0x3b9/0x470 net/socket.c:909
  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
  do_iter_write+0x30d/0xd40 fs/read_write.c:932
  vfs_writev fs/read_write.c:977 [inline]
  do_writev+0x3c9/0x830 fs/read_write.c:1012
  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
  SyS_writev+0x56/0x80 fs/read_write.c:1082
  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43ffa9
RSP: 002b:00007fff2cff3948 EFLAGS: 00000217 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ffa9
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004018d0
R13: 0000000000401960 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
  slab_post_alloc_hook mm/slab.h:445 [inline]
  slab_alloc_node mm/slub.c:2737 [inline]
  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
  __kmalloc_reserve net/core/skbuff.c:138 [inline]
  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
  alloc_skb include/linux/skbuff.h:984 [inline]
  alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
  sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085
  packet_alloc_skb net/packet/af_packet.c:2803 [inline]
  packet_snd net/packet/af_packet.c:2894 [inline]
  packet_sendmsg+0x6444/0x8a10 net/packet/af_packet.c:2969
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg net/socket.c:640 [inline]
  sock_write_iter+0x3b9/0x470 net/socket.c:909
  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
  do_iter_write+0x30d/0xd40 fs/read_write.c:932
  vfs_writev fs/read_write.c:977 [inline]
  do_writev+0x3c9/0x830 fs/read_write.c:1012
  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
  SyS_writev+0x56/0x80 fs/read_write.c:1082
  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x3d/0xa2

Fixes: 58e998c ("offloading: Force software GSO for multiple vlan tags.")
Reported-and-tested-by: [email protected]
Signed-off-by: Toshiaki Makita <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@gregkh
Toshiaki Makita authored and gregkh committed Apr 29, 2018
1 parent dedf29a commit 3f74460
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Showing 2 changed files with 6 additions and 3 deletions.
7 changes: 5 additions & 2 deletions include/linux/if_vlan.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -585,7 +585,7 @@ static inline bool skb_vlan_tagged(const struct sk_buff *skb)
* Returns true if the skb is tagged with multiple vlan headers, regardless
* of whether it is hardware accelerated or not.
*/
static inline bool skb_vlan_tagged_multi(const struct sk_buff *skb)
static inline bool skb_vlan_tagged_multi(struct sk_buff *skb)
{
__be16 protocol = skb->protocol;

Expand All @@ -596,6 +596,9 @@ static inline bool skb_vlan_tagged_multi(const struct sk_buff *skb)
protocol != htons(ETH_P_8021AD)))
return false;

if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN)))
return false;

veh = (struct vlan_ethhdr *)skb->data;
protocol = veh->h_vlan_encapsulated_proto;
}
Expand All @@ -613,7 +616,7 @@ static inline bool skb_vlan_tagged_multi(const struct sk_buff *skb)
*
* Returns features without unsafe ones if the skb has multiple tags.
*/
static inline netdev_features_t vlan_features_check(const struct sk_buff *skb,
static inline netdev_features_t vlan_features_check(struct sk_buff *skb,
netdev_features_t features)
{
if (skb_vlan_tagged_multi(skb)) {
Expand Down
2 changes: 1 addition & 1 deletion net/core/dev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2706,7 +2706,7 @@ netdev_features_t passthru_features_check(struct sk_buff *skb,
}
EXPORT_SYMBOL(passthru_features_check);

static netdev_features_t dflt_features_check(const struct sk_buff *skb,
static netdev_features_t dflt_features_check(struct sk_buff *skb,
struct net_device *dev,
netdev_features_t features)
{
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