CVE-2024-26804

Source
https://nvd.nist.gov/vuln/detail/CVE-2024-26804
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-26804.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2024-26804
Related
Published
2024-04-04T09:15:09Z
Modified
2024-11-12T18:45:22.444418Z
Summary
[none]
Details

In the Linux kernel, the following vulnerability has been resolved:

net: ip_tunnel: prevent perpetual headroom growth

syzkaller triggered following kasan splat: BUG: KASAN: use-after-free in skbflowdissect+0x19d1/0x7a50 net/core/flowdissector.c:1170 Read of size 1 at addr ffff88812fb4000e by task syz-executor183/5191 [..] kasanreport+0xda/0x110 mm/kasan/report.c:588 _skbflowdissect+0x19d1/0x7a50 net/core/flowdissector.c:1170 skbflowdissectflowkeys include/linux/skbuff.h:1514 [inline] skbgethash net/core/flowdissector.c:1791 [inline] _skbgethash+0xc7/0x540 net/core/flowdissector.c:1856 skbgethash include/linux/skbuff.h:1556 [inline] iptunnelxmit+0x1855/0x33c0 net/ipv4/iptunnel.c:748 ipiptunnelxmit+0x3cc/0x4e0 net/ipv4/ipip.c:308 _netdevstartxmit include/linux/netdevice.h:4940 [inline] netdevstartxmit include/linux/netdevice.h:4954 [inline] xmitone net/core/dev.c:3548 [inline] devhardstartxmit+0x13d/0x6d0 net/core/dev.c:3564 _devqueuexmit+0x7c1/0x3d60 net/core/dev.c:4349 devqueuexmit include/linux/netdevice.h:3134 [inline] neighconnectedoutput+0x42c/0x5d0 net/core/neighbour.c:1592 ... ipfinishoutput2+0x833/0x2550 net/ipv4/ipoutput.c:235 ipfinishoutput+0x31/0x310 net/ipv4/ipoutput.c:323 .. iptunnelxmit+0x5b4/0x9b0 net/ipv4/iptunnelcore.c:82 iptunnelxmit+0x1dbc/0x33c0 net/ipv4/iptunnel.c:831 ipgrexmit+0x4a1/0x980 net/ipv4/ipgre.c:665 _netdevstartxmit include/linux/netdevice.h:4940 [inline] netdevstartxmit include/linux/netdevice.h:4954 [inline] xmitone net/core/dev.c:3548 [inline] devhardstartxmit+0x13d/0x6d0 net/core/dev.c:3564 ...

The splat occurs because skb->data points past skb->head allocated area. This is because neigh layer does: _skbpull(skb, skbnetworkoffset(skb));

... but skbnetworkoffset() returns a negative offset and _skbpull() arg is unsigned. IOW, we skb->data gets "adjusted" by a huge value.

The negative value is returned because skb->head and skb->data distance is more than 64k and skb->network_header (u16) has wrapped around.

The bug is in the iptunnel infrastructure, which can cause dev->neededheadroom to increment ad infinitum.

The syzkaller reproducer consists of packets getting routed via a gre tunnel, and route of gre encapsulated packets pointing at another (ipip) tunnel. The ipip encapsulation finds gre0 as next output device.

This results in the following pattern:

1). First packet is to be sent out via gre0. Route lookup found an output device, ipip0.

2). iptunnelxmit for gre0 bumps gre0->neededheadroom based on the future output device, rt.dev->neededheadroom (ipip0).

3). ip output / start_xmit moves skb on to ipip0. which runs the same code path again (xmit recursion).

4). Routing step for the post-gre0-encap packet finds gre0 as output device to use for ipip0 encapsulated packet.

tunl0->needed_headroom is then incremented based on the (already bumped) gre0 device headroom.

This repeats for every future packet:

gre0->neededheadroom gets inflated because previous packets' ipip0 step incremented rt->dev (gre0) headroom, and ipip0 incremented because gre0 neededheadroom was increased.

For each subsequent packet, gre/ipip0->needed_headroom grows until post-expand-head reallocations result in a skb->head/data distance of more than 64k.

Once that happens, skb->networkheader (u16) wraps around when pskbexpandhead tries to make sure that skbnetwork_offset() is unchanged after the headroom expansion/reallocation.

After this skbnetworkoffset(skb) returns a different (and negative) result post headroom expansion.

The next trip to neigh layer (or anything else that would _skbpull the network header) makes skb->data point to a memory location outside skb->head area.

v2: Cap the needed_headroom update to an arbitarily chosen upperlimit to prevent perpetual increase instead of dropping the headroom increment completely.

References

Affected packages

Debian:11 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
5.10.216-1

Affected versions

5.*

5.10.46-4
5.10.46-5
5.10.70-1~bpo10+1
5.10.70-1
5.10.84-1
5.10.92-1~bpo10+1
5.10.92-1
5.10.92-2
5.10.103-1~bpo10+1
5.10.103-1
5.10.106-1
5.10.113-1
5.10.120-1~bpo10+1
5.10.120-1
5.10.127-1
5.10.127-2~bpo10+1
5.10.127-2
5.10.136-1
5.10.140-1
5.10.148-1
5.10.149-1
5.10.149-2
5.10.158-1
5.10.158-2
5.10.162-1
5.10.178-1
5.10.178-2
5.10.178-3
5.10.179-1
5.10.179-2
5.10.179-3
5.10.179-4
5.10.179-5
5.10.191-1
5.10.197-1
5.10.205-1
5.10.205-2
5.10.209-1
5.10.209-2

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:12 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
6.1.82-1

Affected versions

6.*

6.1.27-1
6.1.37-1
6.1.38-1
6.1.38-2~bpo11+1
6.1.38-2
6.1.38-3
6.1.38-4~bpo11+1
6.1.38-4
6.1.52-1
6.1.55-1~bpo11+1
6.1.55-1
6.1.64-1
6.1.66-1
6.1.67-1
6.1.69-1~bpo11+1
6.1.69-1
6.1.76-1~bpo11+1
6.1.76-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:13 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
6.7.9-1

Affected versions

6.*

6.1.27-1
6.1.37-1
6.1.38-1
6.1.38-2~bpo11+1
6.1.38-2
6.1.38-3
6.1.38-4~bpo11+1
6.1.38-4
6.1.52-1
6.1.55-1~bpo11+1
6.1.55-1
6.1.64-1
6.1.66-1
6.1.67-1
6.1.69-1~bpo11+1
6.1.69-1
6.1.76-1~bpo11+1
6.1.76-1
6.1.82-1
6.1.85-1
6.1.90-1~bpo11+1
6.1.90-1
6.1.94-1~bpo11+1
6.1.94-1
6.1.98-1
6.1.99-1
6.1.106-1
6.1.106-2
6.1.106-3
6.1.112-1
6.1.115-1
6.3.1-1~exp1
6.3.2-1~exp1
6.3.4-1~exp1
6.3.5-1~exp1
6.3.7-1~bpo12+1
6.3.7-1
6.3.11-1
6.4~rc6-1~exp1
6.4~rc7-1~exp1
6.4.1-1~exp1
6.4.4-1~bpo12+1
6.4.4-1
6.4.4-2
6.4.4-3~bpo12+1
6.4.4-3
6.4.11-1
6.4.13-1
6.5~rc4-1~exp1
6.5~rc6-1~exp1
6.5~rc7-1~exp1
6.5.1-1~exp1
6.5.3-1~bpo12+1
6.5.3-1
6.5.6-1
6.5.8-1
6.5.10-1~bpo12+1
6.5.10-1
6.5.13-1
6.6.3-1~exp1
6.6.4-1~exp1
6.6.7-1~exp1
6.6.8-1
6.6.9-1
6.6.11-1
6.6.13-1~bpo12+1
6.6.13-1
6.6.15-1
6.6.15-2
6.7-1~exp1
6.7.1-1~exp1
6.7.4-1~exp1
6.7.7-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}