CVE-2024-50042

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

ice: Fix increasing MSI-X on VF

Increasing MSI-X value on a VF leads to invalid memory operations. This is caused by not reallocating some arrays.

Reproducer: modprobe ice echo 0 > /sys/bus/pci/devices/$PF_PCI/sriov_drivers_autoprobe echo 1 > /sys/bus/pci/devices/$PF_PCI/sriov_numvfs echo 17 > /sys/bus/pci/devices/$VF0_PCI/sriov_vf_msix_count

Default MSI-X is 16, so 17 and above triggers this issue.

KASAN reports:

BUG: KASAN: slab-out-of-bounds in ice_vsi_alloc_ring_stats+0x38d/0x4b0 [ice] Read of size 8 at addr ffff8888b937d180 by task bash/28433 (…)

Call Trace: (…) ? ice_vsi_alloc_ring_stats+0x38d/0x4b0 [ice] kasan_report+0xed/0x120 ? ice_vsi_alloc_ring_stats+0x38d/0x4b0 [ice] ice_vsi_alloc_ring_stats+0x38d/0x4b0 [ice] ice_vsi_cfg_def+0x3360/0x4770 [ice] ? mutex_unlock+0x83/0xd0 ? __pfx_ice_vsi_cfg_def+0x10/0x10 [ice] ? __pfx_ice_remove_vsi_lkup_fltr+0x10/0x10 [ice] ice_vsi_cfg+0x7f/0x3b0 [ice] ice_vf_reconfig_vsi+0x114/0x210 [ice] ice_sriov_set_msix_vec_count+0x3d0/0x960 [ice] sriov_vf_msix_count_store+0x21c/0x300 (…)

Allocated by task 28201: (…) ice_vsi_cfg_def+0x1c8e/0x4770 [ice] ice_vsi_cfg+0x7f/0x3b0 [ice] ice_vsi_setup+0x179/0xa30 [ice] ice_sriov_configure+0xcaa/0x1520 [ice] sriov_numvfs_store+0x212/0x390 (…)

To fix it, use ice_vsi_rebuild() instead of ice_vf_reconfig_vsi(). This causes the required arrays to be reallocated taking the new queue count into account (ice_vsi_realloc_stat_arrays()). Set req_txq and req_rxq before ice_vsi_rebuild(), so that realloc uses the newly set queue count.

Additionally, ice_vsi_rebuild() does not remove VSI filters (ice_fltr_remove_all()), so ice_vf_init_host_cfg() is no longer necessary.

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/bce9af1b030bf59d51bbabf909a3ef164787e44e
• https://git.kernel.org/stable/c/cbda6197929418fabf0e45ecf9b7a76360944c70