CVE-2022-50476

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

ntb_netdev: Use dev_kfree_skb_any() in interrupt context

TX/RX callback handlers (ntb_netdev_tx_handler(), ntb_netdev_rx_handler()) can be called in interrupt context via the DMA framework when the respective DMA operations have completed. As such, any calls by these routines to free skbs, should use the interrupt context safe dev_kfree_skb_any() function.

Previously, these callback handlers would call the interrupt unsafe version of dev_kfree_skb(). This has not presented an issue on Intel IOAT DMA engines as that driver utilizes tasklets rather than a hard interrupt handler, like the AMD PTDMA DMA driver. On AMD systems, a kernel WARNING message is encountered, which is being issued from skb_release_head_state() due to in_hardirq() being true.

Besides the user visible WARNING from the kernel, the other symptom of this bug was that TCP/IP performance across the ntb_netdev interface was very poor, i.e. approximately an order of magnitude below what was expected. With the repair to use dev_kfree_skb_any(), kernel WARNINGs from skb_release_head_state() ceased and TCP/IP performance, as measured by iperf, was on par with expected results, approximately 20 Gb/s on AMD Milan based server. Note that this performance is comparable with Intel based servers.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

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/07e28a8f450217db679802ebd4de0915556ce846
• https://git.kernel.org/stable/c/13286ad1c7c49c606fdcba4cf66f953a1a16c1ca
• https://git.kernel.org/stable/c/14d245da57a11e80277ab455aa9b6dcc5ed38a19
• https://git.kernel.org/stable/c/21296a52caa6a6bad6debdfe40ad81d4f1a27e69
• https://git.kernel.org/stable/c/5f7d78b2b12a9d561f48fa00bab29b40f4616dad
• https://git.kernel.org/stable/c/8b78493968ed3cef0326183ed059c55e42f24d5b
• https://git.kernel.org/stable/c/a6b9e09403102bdf8402dae734800e4916c7ea58
• https://git.kernel.org/stable/c/d4460c82177899751975180c268f352893302221
• https://git.kernel.org/stable/c/dd860b39aa7c7b82e6c99b6fdb99d4610ce49d67