CVE-2024-26896

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

wifi: wfx: fix memory leak when starting AP

Kmemleak reported this error:

unreferenced object 0xd73d1180 (size 184):
  comm wpa_supplicant, pid 1559, jiffies 13006305 (age 964.245s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 1e 00 01 00 00 00 00 00  ................
  backtrace:
    [<5ca11420>] kmem_cache_alloc+0x20c/0x5ac
    [<127bdd74>] __alloc_skb+0x144/0x170
    [<fb8a5e38>] __netdev_alloc_skb+0x50/0x180
    [<0f9fa1d5>] __ieee80211_beacon_get+0x290/0x4d4 [mac80211]
    [<7accd02d>] ieee80211_beacon_get_tim+0x54/0x18c [mac80211]
    [<41e25cc3>] wfx_start_ap+0xc8/0x234 [wfx]
    [<93a70356>] ieee80211_start_ap+0x404/0x6b4 [mac80211]
    [<a4a661cd>] nl80211_start_ap+0x76c/0x9e0 [cfg80211]
    [<47bd8b68>] genl_rcv_msg+0x198/0x378
    [<453ef796>] netlink_rcv_skb+0xd0/0x130
    [<6b7c977a>] genl_rcv+0x34/0x44
    [<66b2d04d>] netlink_unicast+0x1b4/0x258
    [<f965b9b6>] netlink_sendmsg+0x1e8/0x428
    [<aadb8231>] ____sys_sendmsg+0x1e0/0x274
    [<d2b5212d>] ___sys_sendmsg+0x80/0xb4
    [<69954f45>] __sys_sendmsg+0x64/0xa8
unreferenced object 0xce087000 (size 1024):
  comm wpa_supplicant, pid 1559, jiffies 13006305 (age 964.246s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    10 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
  backtrace:
    [<9a993714>] __kmalloc_track_caller+0x230/0x600
    [<f83ea192>] kmalloc_reserve.constprop.0+0x30/0x74
    [<a2c61343>] __alloc_skb+0xa0/0x170
    [<fb8a5e38>] __netdev_alloc_skb+0x50/0x180
    [<0f9fa1d5>] __ieee80211_beacon_get+0x290/0x4d4 [mac80211]
    [<7accd02d>] ieee80211_beacon_get_tim+0x54/0x18c [mac80211]
    [<41e25cc3>] wfx_start_ap+0xc8/0x234 [wfx]
    [<93a70356>] ieee80211_start_ap+0x404/0x6b4 [mac80211]
    [<a4a661cd>] nl80211_start_ap+0x76c/0x9e0 [cfg80211]
    [<47bd8b68>] genl_rcv_msg+0x198/0x378
    [<453ef796>] netlink_rcv_skb+0xd0/0x130
    [<6b7c977a>] genl_rcv+0x34/0x44
    [<66b2d04d>] netlink_unicast+0x1b4/0x258
    [<f965b9b6>] netlink_sendmsg+0x1e8/0x428
    [<aadb8231>] ____sys_sendmsg+0x1e0/0x274
    [<d2b5212d>] ___sys_sendmsg+0x80/0xb4

However, since the kernel is build optimized, it seems the stack is not accurate. It appears the issue is related to wfx_set_mfp_ap(). The issue is obvious in this function: memory allocated by ieee80211_beacon_get() is never released. Fixing this leak makes kmemleak happy.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/12f00a367b2b62756e0396f14b54c2c15524e1c3
• https://git.kernel.org/stable/c/3a71ec74e5e3478d202a1874f085ca3ef40be49b
• https://git.kernel.org/stable/c/a1f57a0127b89a6b6620514564aa7eaec16d9af3
• https://git.kernel.org/stable/c/b8cfb7c819dd39965136a66fe3a7fde688d976fc
• https://git.kernel.org/stable/c/dadbb5d29d6c5f571a50272fce8c1505a9559487