CVE-2024-56668

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

iommu/vt-d: Fix qi_batch NULL pointer with nested parent domain

The qi_batch is allocated when assigning cache tag for a domain. While for nested parent domain, it is missed. Hence, when trying to map pages to the nested parent, NULL dereference occurred. Also, there is potential memleak since there is no lock around domain->qi_batch allocation.

To solve it, add a helper for qi_batch allocation, and call it in both the __cache_tag_assign_domain() and __cache_tag_assign_parent_domain().

BUG: kernel NULL pointer dereference, address: 0000000000000200 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 8104795067 P4D 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 223 UID: 0 PID: 4357 Comm: qemu-system-x86 Not tainted 6.13.0-rc1-00028-g4b50c3c3b998-dirty #2632 Call Trace: ? __die+0x24/0x70 ? page_fault_oops+0x80/0x150 ? do_user_addr_fault+0x63/0x7b0 ? exc_page_fault+0x7c/0x220 ? asm_exc_page_fault+0x26/0x30 ? cache_tag_flush_range_np+0x13c/0x260 intel_iommu_iotlb_sync_map+0x1a/0x30 iommu_map+0x61/0xf0 batch_to_domain+0x188/0x250 iopt_area_fill_domains+0x125/0x320 ? rcu_is_watching+0x11/0x50 iopt_map_pages+0x63/0x100 iopt_map_common.isra.0+0xa7/0x190 iopt_map_user_pages+0x6a/0x80 iommufd_ioas_map+0xcd/0x1d0 iommufd_fops_ioctl+0x118/0x1c0 __x64_sys_ioctl+0x93/0xc0 do_syscall_64+0x71/0x140 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/74536f91962d5f6af0a42414773ce61e653c10ee
• https://git.kernel.org/stable/c/ffd774c34774fd4cc0e9cf2976595623a6c3a077