CVE-2024-27005

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

interconnect: Dont access req_list while its being manipulated

The icc_lock mutex was split into separate icc_lock and icc_bw_lock mutexes in [1] to avoid lockdep splats. However, this didnt adequately protect access to icc_node::req_list.

The icc_set_bw() function will eventually iterate over req_list while only holding icc_bw_lock, but req_list can be modified while only holding icc_lock. This causes races between icc_set_bw(), of_icc_get(), and icc_put().

Example A:

CPU0 CPU1

icc_set_bw(path_a) mutex_lock(&icc_bw_lock); icc_put(path_b) mutex_lock(&icc_lock); aggregate_requests() hlist_for_each_entry(r, … hlist_del(… <r = invalid pointer>

Example B:

CPU0 CPU1

icc_set_bw(path_a) mutex_lock(&icc_bw_lock); path_b = of_icc_get() of_icc_get_by_index() mutex_lock(&icc_lock); path_find() path_init() aggregate_requests() hlist_for_each_entry(r, … hlist_add_head(… <r = invalid pointer>

Fix this by ensuring icc_bw_lock is always held before manipulating icc_node::req_list. The additional places icc_bw_lock is held dont perform any memory allocations, so we should still be safe from the original lockdep splats that motivated the separate locks.

[1] commit af42269c3523 (interconnect: Fix locking for runpm vs reclaim)

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/4c65507121ea8e0b47fae6d2049c8688390d46b6
• https://git.kernel.org/stable/c/d0d04efa2e367921654b5106cc5c05e3757c2b42
• https://git.kernel.org/stable/c/de1bf25b6d771abdb52d43546cf57ad775fb68a1
• https://git.kernel.org/stable/c/4c65507121ea8e0b47fae6d2049c8688390d46b6
• https://git.kernel.org/stable/c/d0d04efa2e367921654b5106cc5c05e3757c2b42
• https://git.kernel.org/stable/c/de1bf25b6d771abdb52d43546cf57ad775fb68a1
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4EZ6PJW7VOZ224TD7N4JZNU6KV32ZJ53/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DAMSOZXJEPUOXW33WZYWCVAY7Z5S7OOY/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GCBZZEC7L7KTWWAS2NLJK6SO3IZIL4WW/