ghsa-3g6v-v5hj-c234
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events
After the blamed commit, we started doing this dereference for every NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER event in the system.
static inline struct dsa_port dsa_user_to_port(const struct net_device dev) { struct dsa_user_priv *p = netdev_priv(dev);
return p->dp;
}
Which is obviously bogus, because not all net_devices have a netdev_priv() of type struct dsa_user_priv. But struct dsa_user_priv is fairly small, and p->dp means dereferencing 8 bytes starting with offset 16. Most drivers allocate that much private memory anyway, making our access not fault, and we discard the bogus data quickly afterwards, so this wasn't caught.
But the dummy interface is somewhat special in that it calls alloc_netdev() with a priv size of 0. So every netdev_priv() dereference is invalid, and we get this when we emit a NETDEV_PRECHANGEUPPER event with a VLAN as its new upper:
$ ip link add dummy1 type dummy $ ip link add link dummy1 name dummy1.100 type vlan id 100 [ 43.309174] ================================================================== [ 43.316456] BUG: KASAN: slab-out-of-bounds in dsa_user_prechangeupper+0x30/0xe8 [ 43.323835] Read of size 8 at addr ffff3f86481d2990 by task ip/374 [ 43.330058] [ 43.342436] Call trace: [ 43.366542] dsa_user_prechangeupper+0x30/0xe8 [ 43.371024] dsa_user_netdevice_event+0xb38/0xee8 [ 43.375768] notifier_call_chain+0xa4/0x210 [ 43.379985] raw_notifier_call_chain+0x24/0x38 [ 43.384464] __netdev_upper_dev_link+0x3ec/0x5d8 [ 43.389120] netdev_upper_dev_link+0x70/0xa8 [ 43.393424] register_vlan_dev+0x1bc/0x310 [ 43.397554] vlan_newlink+0x210/0x248 [ 43.401247] rtnl_newlink+0x9fc/0xe30 [ 43.404942] rtnetlink_rcv_msg+0x378/0x580
Avoid the kernel oops by dereferencing after the type check, as customary.
{
"affected": [],
"aliases": [
"CVE-2024-26596"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-02-23T15:15:09Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events\n\nAfter the blamed commit, we started doing this dereference for every\nNETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER event in the system.\n\nstatic inline struct dsa_port *dsa_user_to_port(const struct net_device *dev)\n{\n\tstruct dsa_user_priv *p = netdev_priv(dev);\n\n\treturn p-\u003edp;\n}\n\nWhich is obviously bogus, because not all net_devices have a netdev_priv()\nof type struct dsa_user_priv. But struct dsa_user_priv is fairly small,\nand p-\u003edp means dereferencing 8 bytes starting with offset 16. Most\ndrivers allocate that much private memory anyway, making our access not\nfault, and we discard the bogus data quickly afterwards, so this wasn\u0027t\ncaught.\n\nBut the dummy interface is somewhat special in that it calls\nalloc_netdev() with a priv size of 0. So every netdev_priv() dereference\nis invalid, and we get this when we emit a NETDEV_PRECHANGEUPPER event\nwith a VLAN as its new upper:\n\n$ ip link add dummy1 type dummy\n$ ip link add link dummy1 name dummy1.100 type vlan id 100\n[ 43.309174] ==================================================================\n[ 43.316456] BUG: KASAN: slab-out-of-bounds in dsa_user_prechangeupper+0x30/0xe8\n[ 43.323835] Read of size 8 at addr ffff3f86481d2990 by task ip/374\n[ 43.330058]\n[ 43.342436] Call trace:\n[ 43.366542] dsa_user_prechangeupper+0x30/0xe8\n[ 43.371024] dsa_user_netdevice_event+0xb38/0xee8\n[ 43.375768] notifier_call_chain+0xa4/0x210\n[ 43.379985] raw_notifier_call_chain+0x24/0x38\n[ 43.384464] __netdev_upper_dev_link+0x3ec/0x5d8\n[ 43.389120] netdev_upper_dev_link+0x70/0xa8\n[ 43.393424] register_vlan_dev+0x1bc/0x310\n[ 43.397554] vlan_newlink+0x210/0x248\n[ 43.401247] rtnl_newlink+0x9fc/0xe30\n[ 43.404942] rtnetlink_rcv_msg+0x378/0x580\n\nAvoid the kernel oops by dereferencing after the type check, as customary.",
"id": "GHSA-3g6v-v5hj-c234",
"modified": "2024-10-10T12:31:11Z",
"published": "2024-02-23T15:30:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26596"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/69a1e2d938dbbfcff0e064269adf60ad26dbb102"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/844f104790bd69c2e4dbb9ee3eba46fde1fcea7b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dbd909c20c11f0d29c0054d41e0d1f668a60e8c8"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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