linux.git/net/ipv4/ip_gre.c, branch v6.14 Linux kernel source tree gre: Prepare ipgre_open() to .flowi4_tos conversion. 2025-01-17T00:51:57+00:00 Guillaume Nault gnault@redhat.com 2025-01-15T11:53:55+00:00 2c77bcb344f589054b2039bddcd32c4f666258b9 Use ip4h_dscp() to get the tunnel DSCP option as dscp_t, instead of manually masking the raw tos field with INET_DSCP_MASK. This will ease the conversion of fl4->flowi4_tos to dscp_t, which just becomes a matter of dropping the inet_dscp_to_dsfield() call. Signed-off-by: Guillaume Nault <gnault@redhat.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/6c05a11afdc61530f1a4505147e0909ad51feb15.1736941806.git.gnault@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Use ip4h_dscp() to get the tunnel DSCP option as dscp_t, instead of
manually masking the raw tos field with INET_DSCP_MASK. This will ease
the conversion of fl4->flowi4_tos to dscp_t, which just becomes a
matter of dropping the inet_dscp_to_dsfield() call.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/6c05a11afdc61530f1a4505147e0909ad51feb15.1736941806.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
gre: Drop ip_route_output_gre(). 2024-12-20T03:24:47+00:00 Guillaume Nault gnault@redhat.com 2024-12-18T13:17:16+00:00 29b540795b42a3e610c0d5e9d908a8d6c1333676 We already have enough variants of ip_route_output*() functions. We don't need a GRE specific one in the generic route.h header file. Furthermore, ip_route_output_gre() is only used once, in ipgre_open(), where it can be easily replaced by a simple call to ip_route_output_key(). While there, and for clarity, explicitly set .flowi4_scope to RT_SCOPE_UNIVERSE instead of relying on the implicit zero initialisation. Signed-off-by: Guillaume Nault <gnault@redhat.com> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com> Link: https://patch.msgid.link/ab7cba47b8558cd4bfe2dc843c38b622a95ee48e.1734527729.git.gnault@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
We already have enough variants of ip_route_output*() functions. We
don't need a GRE specific one in the generic route.h header file.

Furthermore, ip_route_output_gre() is only used once, in ipgre_open(),
where it can be easily replaced by a simple call to
ip_route_output_key().

While there, and for clarity, explicitly set .flowi4_scope to
RT_SCOPE_UNIVERSE instead of relying on the implicit zero
initialisation.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/ab7cba47b8558cd4bfe2dc843c38b622a95ee48e.1734527729.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
ipv4: ip_gre: Fix drops of small packets in ipgre_xmit 2024-10-01T11:04:03+00:00 Anton Danilov littlesmilingcloud@gmail.com 2024-09-24T23:51:59+00:00 c4a14f6d9d17ad1e41a36182dd3b8a5fd91efbd7 Regression Description: Depending on the options specified for the GRE tunnel device, small packets may be dropped. This occurs because the pskb_network_may_pull function fails due to the packet's insufficient length. For example, if only the okey option is specified for the tunnel device, original (before encapsulation) packets smaller than 28 bytes (including the IPv4 header) will be dropped. This happens because the required length is calculated relative to the network header, not the skb->head. Here is how the required length is computed and checked: * The pull_len variable is set to 28 bytes, consisting of: * IPv4 header: 20 bytes * GRE header with Key field: 8 bytes * The pskb_network_may_pull function adds the network offset, shifting the checkable space further to the beginning of the network header and extending it to the beginning of the packet. As a result, the end of the checkable space occurs beyond the actual end of the packet. Instead of ensuring that 28 bytes are present in skb->head, the function is requesting these 28 bytes starting from the network header. For small packets, this requested length exceeds the actual packet size, causing the check to fail and the packets to be dropped. This issue affects both locally originated and forwarded packets in DMVPN-like setups. How to reproduce (for local originated packets): ip link add dev gre1 type gre ikey 1.9.8.4 okey 1.9.8.4 \ local <your-ip> remote 0.0.0.0 ip link set mtu 1400 dev gre1 ip link set up dev gre1 ip address add 192.168.13.1/24 dev gre1 ip neighbor add 192.168.13.2 lladdr <remote-ip> dev gre1 ping -s 1374 -c 10 192.168.13.2 tcpdump -vni gre1 tcpdump -vni <your-ext-iface> 'ip proto 47' ip -s -s -d link show dev gre1 Solution: Use the pskb_may_pull function instead the pskb_network_may_pull. Fixes: 80d875cfc9d3 ("ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()") Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20240924235158.106062-1-littlesmilingcloud@gmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
Regression Description:

Depending on the options specified for the GRE tunnel device, small
packets may be dropped. This occurs because the pskb_network_may_pull
function fails due to the packet's insufficient length.

For example, if only the okey option is specified for the tunnel device,
original (before encapsulation) packets smaller than 28 bytes (including
the IPv4 header) will be dropped. This happens because the required
length is calculated relative to the network header, not the skb->head.

Here is how the required length is computed and checked:

* The pull_len variable is set to 28 bytes, consisting of:
  * IPv4 header: 20 bytes
  * GRE header with Key field: 8 bytes

* The pskb_network_may_pull function adds the network offset, shifting
the checkable space further to the beginning of the network header and
extending it to the beginning of the packet. As a result, the end of
the checkable space occurs beyond the actual end of the packet.

Instead of ensuring that 28 bytes are present in skb->head, the function
is requesting these 28 bytes starting from the network header. For small
packets, this requested length exceeds the actual packet size, causing
the check to fail and the packets to be dropped.

This issue affects both locally originated and forwarded packets in
DMVPN-like setups.

How to reproduce (for local originated packets):

  ip link add dev gre1 type gre ikey 1.9.8.4 okey 1.9.8.4 \
          local <your-ip> remote 0.0.0.0

  ip link set mtu 1400 dev gre1
  ip link set up dev gre1
  ip address add 192.168.13.1/24 dev gre1
  ip neighbor add 192.168.13.2 lladdr <remote-ip> dev gre1
  ping -s 1374 -c 10 192.168.13.2
  tcpdump -vni gre1
  tcpdump -vni <your-ext-iface> 'ip proto 47'
  ip -s -s -d link show dev gre1

Solution:

Use the pskb_may_pull function instead the pskb_network_may_pull.

Fixes: 80d875cfc9d3 ("ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()")
Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20240924235158.106062-1-littlesmilingcloud@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
ipv4: ip_gre: Unmask upper DSCP bits in ipgre_open() 2024-09-09T13:14:52+00:00 Ido Schimmel idosch@nvidia.com 2024-09-05T16:51:30+00:00 25376a890119b616d5982c8cb59f805138ab81fa Unmask the upper DSCP bits when calling ip_route_output_gre() so that in the future it could perform the FIB lookup according to the full DSCP value. Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Guillaume Nault <gnault@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
Unmask the upper DSCP bits when calling ip_route_output_gre() so that in
the future it could perform the FIB lookup according to the full DSCP
value.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
netdev_features: convert NETIF_F_LLTX to dev->lltx 2024-09-03T09:36:43+00:00 Alexander Lobakin aleksander.lobakin@intel.com 2024-08-29T12:33:37+00:00 00d066a4d4edbe559ba6c35153da71d4b2b8a383 NETIF_F_LLTX can't be changed via Ethtool and is not a feature, rather an attribute, very similar to IFF_NO_QUEUE (and hot). Free one netdev_features_t bit and make it a "hot" private flag. Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
NETIF_F_LLTX can't be changed via Ethtool and is not a feature,
rather an attribute, very similar to IFF_NO_QUEUE (and hot).
Free one netdev_features_t bit and make it a "hot" private flag.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
net: annotate writes on dev->mtu from ndo_change_mtu() 2024-05-07T23:19:14+00:00 Eric Dumazet edumazet@google.com 2024-05-06T10:28:12+00:00 1eb2cded45b35816085c1f962933c187d970f9dc Simon reported that ndo_change_mtu() methods were never updated to use WRITE_ONCE(dev->mtu, new_mtu) as hinted in commit 501a90c94510 ("inet: protect against too small mtu values.") We read dev->mtu without holding RTNL in many places, with READ_ONCE() annotations. It is time to take care of ndo_change_mtu() methods to use corresponding WRITE_ONCE() Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Simon Horman <horms@kernel.org> Closes: https://lore.kernel.org/netdev/20240505144608.GB67882@kernel.org/ Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Sabrina Dubroca <sd@queasysnail.net> Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Shannon Nelson <shannon.nelson@amd.com> Link: https://lore.kernel.org/r/20240506102812.3025432-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Simon reported that ndo_change_mtu() methods were never
updated to use WRITE_ONCE(dev->mtu, new_mtu) as hinted
in commit 501a90c94510 ("inet: protect against too small
mtu values.")

We read dev->mtu without holding RTNL in many places,
with READ_ONCE() annotations.

It is time to take care of ndo_change_mtu() methods
to use corresponding WRITE_ONCE()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Simon Horman <horms@kernel.org>
Closes: https://lore.kernel.org/netdev/20240505144608.GB67882@kernel.org/
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Shannon Nelson <shannon.nelson@amd.com>
Link: https://lore.kernel.org/r/20240506102812.3025432-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2024-04-05T01:01:07+00:00 Jakub Kicinski kuba@kernel.org 2024-04-05T00:03:18+00:00 cf1ca1f66d301a55ab8e79188ddf347a8d011e35 Cross-merge networking fixes after downstream PR. Conflicts: net/ipv4/ip_gre.c 17af420545a7 ("erspan: make sure erspan_base_hdr is present in skb->head") 5832c4a77d69 ("ip_tunnel: convert __be16 tunnel flags to bitmaps") https://lore.kernel.org/all/20240402103253.3b54a1cf@canb.auug.org.au/ Adjacent changes: net/ipv6/ip6_fib.c d21d40605bca ("ipv6: Fix infinite recursion in fib6_dump_done().") 5fc68320c1fb ("ipv6: remove RTNL protection from inet6_dump_fib()") Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cross-merge networking fixes after downstream PR.

Conflicts:

net/ipv4/ip_gre.c
  17af420545a7 ("erspan: make sure erspan_base_hdr is present in skb->head")
  5832c4a77d69 ("ip_tunnel: convert __be16 tunnel flags to bitmaps")
https://lore.kernel.org/all/20240402103253.3b54a1cf@canb.auug.org.au/

Adjacent changes:

net/ipv6/ip6_fib.c
  d21d40605bca ("ipv6: Fix infinite recursion in fib6_dump_done().")
  5fc68320c1fb ("ipv6: remove RTNL protection from inet6_dump_fib()")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
ip_tunnel: convert __be16 tunnel flags to bitmaps 2024-04-01T09:49:28+00:00 Alexander Lobakin aleksander.lobakin@intel.com 2024-03-27T15:23:53+00:00 5832c4a77d6931cebf9ba737129ae8f14b66ee1d Historically, tunnel flags like TUNNEL_CSUM or TUNNEL_ERSPAN_OPT have been defined as __be16. Now all of those 16 bits are occupied and there's no more free space for new flags. It can't be simply switched to a bigger container with no adjustments to the values, since it's an explicit Endian storage, and on LE systems (__be16)0x0001 equals to (__be64)0x0001000000000000. We could probably define new 64-bit flags depending on the Endianness, i.e. (__be64)0x0001 on BE and (__be64)0x00010000... on LE, but that would introduce an Endianness dependency and spawn a ton of Sparse warnings. To mitigate them, all of those places which were adjusted with this change would be touched anyway, so why not define stuff properly if there's no choice. Define IP_TUNNEL_*_BIT counterparts as a bit number instead of the value already coded and a fistful of <16 <-> bitmap> converters and helpers. The two flags which have a different bit position are SIT_ISATAP_BIT and VTI_ISVTI_BIT, as they were defined not as __cpu_to_be16(), but as (__force __be16), i.e. had different positions on LE and BE. Now they both have strongly defined places. Change all __be16 fields which were used to store those flags, to IP_TUNNEL_DECLARE_FLAGS() -> DECLARE_BITMAP(__IP_TUNNEL_FLAG_NUM) -> unsigned long[1] for now, and replace all TUNNEL_* occurrences to their bitmap counterparts. Use the converters in the places which talk to the userspace, hardware (NFP) or other hosts (GRE header). The rest must explicitly use the new flags only. This must be done at once, otherwise there will be too many conversions throughout the code in the intermediate commits. Finally, disable the old __be16 flags for use in the kernel code (except for the two 'irregular' flags mentioned above), to prevent any accidental (mis)use of them. For the userspace, nothing is changed, only additions were made. Most noticeable bloat-o-meter difference (.text): vmlinux: 307/-1 (306) gre.ko: 62/0 (62) ip_gre.ko: 941/-217 (724) [*] ip_tunnel.ko: 390/-900 (-510) [**] ip_vti.ko: 138/0 (138) ip6_gre.ko: 534/-18 (516) [*] ip6_tunnel.ko: 118/-10 (108) [*] gre_flags_to_tnl_flags() grew, but still is inlined [**] ip_tunnel_find() got uninlined, hence such decrease The average code size increase in non-extreme case is 100-200 bytes per module, mostly due to sizeof(long) > sizeof(__be16), as %__IP_TUNNEL_FLAG_NUM is less than %BITS_PER_LONG and the compilers are able to expand the majority of bitmap_*() calls here into direct operations on scalars. Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
Historically, tunnel flags like TUNNEL_CSUM or TUNNEL_ERSPAN_OPT
have been defined as __be16. Now all of those 16 bits are occupied
and there's no more free space for new flags.
It can't be simply switched to a bigger container with no
adjustments to the values, since it's an explicit Endian storage,
and on LE systems (__be16)0x0001 equals to
(__be64)0x0001000000000000.
We could probably define new 64-bit flags depending on the
Endianness, i.e. (__be64)0x0001 on BE and (__be64)0x00010000... on
LE, but that would introduce an Endianness dependency and spawn a
ton of Sparse warnings. To mitigate them, all of those places which
were adjusted with this change would be touched anyway, so why not
define stuff properly if there's no choice.

Define IP_TUNNEL_*_BIT counterparts as a bit number instead of the
value already coded and a fistful of <16 <-> bitmap> converters and
helpers. The two flags which have a different bit position are
SIT_ISATAP_BIT and VTI_ISVTI_BIT, as they were defined not as
__cpu_to_be16(), but as (__force __be16), i.e. had different
positions on LE and BE. Now they both have strongly defined places.
Change all __be16 fields which were used to store those flags, to
IP_TUNNEL_DECLARE_FLAGS() -> DECLARE_BITMAP(__IP_TUNNEL_FLAG_NUM) ->
unsigned long[1] for now, and replace all TUNNEL_* occurrences to
their bitmap counterparts. Use the converters in the places which talk
to the userspace, hardware (NFP) or other hosts (GRE header). The rest
must explicitly use the new flags only. This must be done at once,
otherwise there will be too many conversions throughout the code in
the intermediate commits.
Finally, disable the old __be16 flags for use in the kernel code
(except for the two 'irregular' flags mentioned above), to prevent
any accidental (mis)use of them. For the userspace, nothing is
changed, only additions were made.

Most noticeable bloat-o-meter difference (.text):

vmlinux:	307/-1 (306)
gre.ko:		62/0 (62)
ip_gre.ko:	941/-217 (724)	[*]
ip_tunnel.ko:	390/-900 (-510)	[**]
ip_vti.ko:	138/0 (138)
ip6_gre.ko:	534/-18 (516)	[*]
ip6_tunnel.ko:	118/-10 (108)

[*] gre_flags_to_tnl_flags() grew, but still is inlined
[**] ip_tunnel_find() got uninlined, hence such decrease

The average code size increase in non-extreme case is 100-200 bytes
per module, mostly due to sizeof(long) > sizeof(__be16), as
%__IP_TUNNEL_FLAG_NUM is less than %BITS_PER_LONG and the compilers
are able to expand the majority of bitmap_*() calls here into direct
operations on scalars.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ip_tunnel: use a separate struct to store tunnel params in the kernel 2024-04-01T09:49:28+00:00 Alexander Lobakin aleksander.lobakin@intel.com 2024-03-27T15:23:52+00:00 117aef12a7b1b797bce9f66b156c65eab850b5b5 Unlike IPv6 tunnels which use purely-kernel __ip6_tnl_parm structure to store params inside the kernel, IPv4 tunnel code uses the same ip_tunnel_parm which is being used to talk with the userspace. This makes it difficult to alter or add any fields or use a different format for whatever data. Define struct ip_tunnel_parm_kern, a 1:1 copy of ip_tunnel_parm for now, and use it throughout the code. Define the pieces, where the copy user <-> kernel happens, as standalone functions, and copy the data there field-by-field, so that the kernel-side structure could be easily modified later on and the users wouldn't have to care about this. Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
Unlike IPv6 tunnels which use purely-kernel __ip6_tnl_parm structure
to store params inside the kernel, IPv4 tunnel code uses the same
ip_tunnel_parm which is being used to talk with the userspace.
This makes it difficult to alter or add any fields or use a
different format for whatever data.
Define struct ip_tunnel_parm_kern, a 1:1 copy of ip_tunnel_parm for
now, and use it throughout the code. Define the pieces, where the copy
user <-> kernel happens, as standalone functions, and copy the data
there field-by-field, so that the kernel-side structure could be easily
modified later on and the users wouldn't have to care about this.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
erspan: make sure erspan_base_hdr is present in skb->head 2024-03-29T19:42:55+00:00 Eric Dumazet edumazet@google.com 2024-03-28T11:22:48+00:00 17af420545a750f763025149fa7b833a4fc8b8f0 syzbot reported a problem in ip6erspan_rcv() [1] Issue is that ip6erspan_rcv() (and erspan_rcv()) no longer make sure erspan_base_hdr is present in skb linear part (skb->head) before getting @ver field from it. Add the missing pskb_may_pull() calls. v2: Reload iph pointer in erspan_rcv() after pskb_may_pull() because skb->head might have changed. [1] BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2742 [inline] BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2756 [inline] BUG: KMSAN: uninit-value in ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline] BUG: KMSAN: uninit-value in gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610 pskb_may_pull_reason include/linux/skbuff.h:2742 [inline] pskb_may_pull include/linux/skbuff.h:2756 [inline] ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline] gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610 ip6_protocol_deliver_rcu+0x1d4c/0x2ca0 net/ipv6/ip6_input.c:438 ip6_input_finish net/ipv6/ip6_input.c:483 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492 ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586 dst_input include/net/dst.h:460 [inline] ip6_rcv_finish+0x955/0x970 net/ipv6/ip6_input.c:79 NF_HOOK include/linux/netfilter.h:314 [inline] ipv6_rcv+0xde/0x390 net/ipv6/ip6_input.c:310 __netif_receive_skb_one_core net/core/dev.c:5538 [inline] __netif_receive_skb+0x1da/0xa00 net/core/dev.c:5652 netif_receive_skb_internal net/core/dev.c:5738 [inline] netif_receive_skb+0x58/0x660 net/core/dev.c:5798 tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1549 tun_get_user+0x5566/0x69e0 drivers/net/tun.c:2002 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048 call_write_iter include/linux/fs.h:2108 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0xb63/0x1520 fs/read_write.c:590 ksys_write+0x20f/0x4c0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x93/0xe0 fs/read_write.c:652 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 Uninit was created at: slab_post_alloc_hook mm/slub.c:3804 [inline] slab_alloc_node mm/slub.c:3845 [inline] kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577 __alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668 alloc_skb include/linux/skbuff.h:1318 [inline] alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504 sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795 tun_alloc_skb drivers/net/tun.c:1525 [inline] tun_get_user+0x209a/0x69e0 drivers/net/tun.c:1846 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048 call_write_iter include/linux/fs.h:2108 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0xb63/0x1520 fs/read_write.c:590 ksys_write+0x20f/0x4c0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x93/0xe0 fs/read_write.c:652 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 CPU: 1 PID: 5045 Comm: syz-executor114 Not tainted 6.9.0-rc1-syzkaller-00021-g962490525cff #0 Fixes: cb73ee40b1b3 ("net: ip_gre: use erspan key field for tunnel lookup") Reported-by: syzbot+1c1cf138518bf0c53d68@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/000000000000772f2c0614b66ef7@google.com/ Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Lorenzo Bianconi <lorenzo@kernel.org> Link: https://lore.kernel.org/r/20240328112248.1101491-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
syzbot reported a problem in ip6erspan_rcv() [1]

Issue is that ip6erspan_rcv() (and erspan_rcv()) no longer make
sure erspan_base_hdr is present in skb linear part (skb->head)
before getting @ver field from it.

Add the missing pskb_may_pull() calls.

v2: Reload iph pointer in erspan_rcv() after pskb_may_pull()
    because skb->head might have changed.

[1]

 BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
 BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2756 [inline]
 BUG: KMSAN: uninit-value in ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
 BUG: KMSAN: uninit-value in gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
  pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
  pskb_may_pull include/linux/skbuff.h:2756 [inline]
  ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
  gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
  ip6_protocol_deliver_rcu+0x1d4c/0x2ca0 net/ipv6/ip6_input.c:438
  ip6_input_finish net/ipv6/ip6_input.c:483 [inline]
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492
  ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586
  dst_input include/net/dst.h:460 [inline]
  ip6_rcv_finish+0x955/0x970 net/ipv6/ip6_input.c:79
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ipv6_rcv+0xde/0x390 net/ipv6/ip6_input.c:310
  __netif_receive_skb_one_core net/core/dev.c:5538 [inline]
  __netif_receive_skb+0x1da/0xa00 net/core/dev.c:5652
  netif_receive_skb_internal net/core/dev.c:5738 [inline]
  netif_receive_skb+0x58/0x660 net/core/dev.c:5798
  tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1549
  tun_get_user+0x5566/0x69e0 drivers/net/tun.c:2002
  tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
  call_write_iter include/linux/fs.h:2108 [inline]
  new_sync_write fs/read_write.c:497 [inline]
  vfs_write+0xb63/0x1520 fs/read_write.c:590
  ksys_write+0x20f/0x4c0 fs/read_write.c:643
  __do_sys_write fs/read_write.c:655 [inline]
  __se_sys_write fs/read_write.c:652 [inline]
  __x64_sys_write+0x93/0xe0 fs/read_write.c:652
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:
  slab_post_alloc_hook mm/slub.c:3804 [inline]
  slab_alloc_node mm/slub.c:3845 [inline]
  kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888
  kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
  __alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668
  alloc_skb include/linux/skbuff.h:1318 [inline]
  alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504
  sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795
  tun_alloc_skb drivers/net/tun.c:1525 [inline]
  tun_get_user+0x209a/0x69e0 drivers/net/tun.c:1846
  tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
  call_write_iter include/linux/fs.h:2108 [inline]
  new_sync_write fs/read_write.c:497 [inline]
  vfs_write+0xb63/0x1520 fs/read_write.c:590
  ksys_write+0x20f/0x4c0 fs/read_write.c:643
  __do_sys_write fs/read_write.c:655 [inline]
  __se_sys_write fs/read_write.c:652 [inline]
  __x64_sys_write+0x93/0xe0 fs/read_write.c:652
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

CPU: 1 PID: 5045 Comm: syz-executor114 Not tainted 6.9.0-rc1-syzkaller-00021-g962490525cff #0

Fixes: cb73ee40b1b3 ("net: ip_gre: use erspan key field for tunnel lookup")
Reported-by: syzbot+1c1cf138518bf0c53d68@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/000000000000772f2c0614b66ef7@google.com/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/20240328112248.1101491-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>