Security Leftovers
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Security updates for Thursday
Security updates have been issued by Gentoo (aiohttp, faac, isync, motion, and nextcloud), Red Hat (.NET 6.0), SUSE (libnbd, oracleasm, python-codecov, rubygem-tzinfo, sssd, and thunderbird), and Ubuntu (http-parser, linux, linux-aws, linux-aws-5.4, linux-azure, linux-azure-5.4, linux-bluefield, linux-gcp, linux-gcp-5.4, linux-gke, linux-gke-5.4, linux-gkeop, linux-gkeop-5.4, linux-hwe-5.4, linux-ibm, linux-ibm-5.4, linux-kvm, linux-oracle, linux-oracle-5.4, linux-raspi, linux-raspi-5.4, linux, linux-hwe-5.15, linux-lowlatency, linux-lowlatency-hwe-5.15, linux-aws, linux-aws-5.15, linux-azure, linux-azure-5.15, linux-gcp, linux-gcp-5.15, linux-gke, linux-gke-5.15, linux-ibm, linux-kvm, linux-oracle, linux-raspi, linux-intel-iotg, linux-oem-5.14, linux-oem-5.17, and node-moment).
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CISA Issues Warning on Active Exploitation of UnRAR Software for Linux Systems [Ed: How to distract from the major problem CISA has just pointed out]
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PyPI Package 'secretslib' Drops Fileless Linux Malware to Mine Monero [Ed: The issue here is not "Linux" but people installing malware on it]
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The quantum state of Linux kernel garbage collection (Project Zero) [LWN.net]
The Project Zero blog has posted a detailed look at CVE-2021-0920 in the first of a two-part series on how this bug created a vulnerability that was subsequently exploited.
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Security requirements for new kernel features [LWN.net]
The relatively new io_uring subsystem has changed the way asynchronous I/O is done on Linux systems and improved performance significantly. It has also, however, begun to run up a record of disagreements with the kernel's security community. A recent discussion about security hooks for the new uring_cmd mechanism shows how easily requirements can be overlooked in a complex system with no overall supervision.
Most of the operations that can be performed within io_uring follow the usual I/O patterns — open a file, read data, write data, and so on. These operations are the same regardless of the underlying device or filesystem that is doing the work. There always seems to be a need for something special and device-specific, though, and io_uring is no exception. For the kernel as a whole, device-specific operations are made available via ioctl() calls. That system call, however, has built up a reputation as a dumping ground for poorly thought-out features, and there is little desire to see its usage spread.
In early 2021, io_uring maintainer Jens Axboe floated an idea for a command passthrough mechanism that would be specific to io_uring. A year and some later, that idea has evolved into uring_cmd, which was pulled into the mainline during the 5.19 merge window. There is a new io_uring operation that, in turn, causes an invocation of the underlying device or filesystem's uring_cmd() file_operations function. The actual operation to be performed is passed through to that function with no interpretation in the io_uring layer. The first user is the NVMe driver, which provides a direct passthrough operation.