CVE-2022-49667

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

net: bonding: fix use-after-free after 802.3ad slave unbind

commit 0622cab0341c (bonding: fix 802.3ad aggregator reselection), resolve case, when there is several aggregation groups in the same bond. bond_3ad_unbind_slave will invalidate (clear) aggregator when __agg_active_ports return zero. So, ad_clear_agg can be executed even, when num_of_ports!=0. Than bond_3ad_unbind_slave can be executed again for, previously cleared aggregator. NOTE: at this time bond_3ad_unbind_slave will not update slave ports list, because lag_ports==NULL. So, here we got slave ports, pointing to freed aggregator memory.

Fix with checking actual number of ports in group (as was before commit 0622cab0341c (bonding: fix 802.3ad aggregator reselection) ), before ad_clear_agg().

The KASAN logs are as follows:

[ 767.617392] ================================================================== [ 767.630776] BUG: KASAN: use-after-free in bond_3ad_state_machine_handler+0x13dc/0x1470 [ 767.638764] Read of size 2 at addr ffff00011ba9d430 by task kworker/u8:7/767 [ 767.647361] CPU: 3 PID: 767 Comm: kworker/u8:7 Tainted: G O 5.15.11 #15 [ 767.655329] Hardware name: DNI AmazonGo1 A7040 board (DT) [ 767.660760] Workqueue: lacp_1 bond_3ad_state_machine_handler [ 767.666468] Call trace: [ 767.668930] dump_backtrace+0x0/0x2d0 [ 767.672625] show_stack+0x24/0x30 [ 767.675965] dump_stack_lvl+0x68/0x84 [ 767.679659] print_address_description.constprop.0+0x74/0x2b8 [ 767.685451] kasan_report+0x1f0/0x260 [ 767.689148] __asan_load2+0x94/0xd0 [ 767.692667] bond_3ad_state_machine_handler+0x13dc/0x1470

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/050133e1aa2cb49bb17be847d48a4431598ef562
• https://git.kernel.org/stable/c/2765749def4765c5052a4c66445cf4c96fcccdbc
• https://git.kernel.org/stable/c/63b2fe509f69b90168a75e04e14573dccf7984e6
• https://git.kernel.org/stable/c/893825289ba840afd86bfffcb6f7f363c73efff8
• https://git.kernel.org/stable/c/a853b7a3a9fd1d74a4ccdd9cd73512b7dace2f1e
• https://git.kernel.org/stable/c/b90ac60303063a43e17dd4aec159067599d255e6
• https://git.kernel.org/stable/c/ef0af7d08d26c5333ff4944a559279464edf6f15
• https://git.kernel.org/stable/c/f162f7c348fa2a5555bafdb5cc890b89b221e69c