CVE-2024-35855

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

mlxsw: spectrum_acl_tcam: Fix possible use-after-free during activity update

The rule activity update delayed work periodically traverses the list of configured rules and queries their activity from the device.

As part of this task it accesses the entry pointed by ventry->entry, but this entry can be changed concurrently by the rehash delayed work, leading to a use-after-free [1].

Fix by closing the race and perform the activity query under the vregion->lock mutex.

[1] BUG: KASAN: slab-use-after-free in mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140 Read of size 8 at addr ffff8881054ed808 by task kworker/0:18/181

CPU: 0 PID: 181 Comm: kworker/0:18 Not tainted 6.9.0-rc2-custom-00781-gd5ab772d32f7 #2 Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019 Workqueue: mlxsw_core mlxsw_sp_acl_rule_activity_update_work Call Trace: dump_stack_lvl+0xc6/0x120 print_report+0xce/0x670 kasan_report+0xd7/0x110 mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140 mlxsw_sp_acl_rule_activity_update_work+0x219/0x400 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30

Allocated by task 1039: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x8f/0xa0 __kmalloc+0x19c/0x360 mlxsw_sp_acl_tcam_entry_create+0x7b/0x1f0 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x30d/0xb50 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30

Freed by task 1039: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 poison_slab_object+0x102/0x170 __kasan_slab_free+0x14/0x30 kfree+0xc1/0x290 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x3d7/0xb50 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30

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/1b73f6e4ea770410a937a8db98f77e52594d23a0
• https://git.kernel.org/stable/c/79b5b4b18bc85b19d3a518483f9abbbe6d7b3ba4
• https://git.kernel.org/stable/c/b183b915beef818a25e3154d719ca015a1ae0770
• https://git.kernel.org/stable/c/b996e8699da810e4c915841d6aaef761007f933a
• https://git.kernel.org/stable/c/c17976b42d546ee118ca300db559630ee96fb758
• https://git.kernel.org/stable/c/e24d2487424779c02760ff50cd9021b8676e19ef
• https://git.kernel.org/stable/c/feabdac2057e863d0e140a2adf3d232eb4882db4
• https://git.kernel.org/stable/c/1b73f6e4ea770410a937a8db98f77e52594d23a0
• https://git.kernel.org/stable/c/79b5b4b18bc85b19d3a518483f9abbbe6d7b3ba4
• https://git.kernel.org/stable/c/b183b915beef818a25e3154d719ca015a1ae0770
• https://git.kernel.org/stable/c/b996e8699da810e4c915841d6aaef761007f933a
• https://git.kernel.org/stable/c/c17976b42d546ee118ca300db559630ee96fb758
• https://git.kernel.org/stable/c/e24d2487424779c02760ff50cd9021b8676e19ef
• https://git.kernel.org/stable/c/feabdac2057e863d0e140a2adf3d232eb4882db4
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html