CVE-2022-2209 in Linux
Summary
by MITRE • 07/22/2022
io_uring uses work_flags to determine which identity need to grab from the calling process to make sure it is consistent with the calling process when executing IORING_OP. The mapping of flags is incomplete, which leads to multiple incorrect reference counts and hence use-after-free. We recommend upgrading past commit df3f3bb5059d20ef094d6b2f0256c4bf4127a859
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Analysis
by VulDB Data Team • 07/22/2022
The io_uring subsystem in the Linux kernel presents a critical vulnerability through an incomplete flag mapping mechanism that compromises memory safety and process consistency. This vulnerability specifically affects the work_flags implementation used to determine which identity should be retrieved from the calling process during IORING_OP execution. The flaw manifests when the kernel fails to properly map all relevant flags, creating a scenario where reference counts become inconsistent across multiple execution contexts. This incomplete mapping directly impacts the kernel's ability to maintain proper ownership semantics for I/O operations, leading to situations where memory objects may be freed while still referenced by other processes or threads.
The technical implementation of this vulnerability stems from the io_uring driver's insufficient handling of work_flags during asynchronous I/O operation processing. When a process submits an IORING_OP operation, the kernel must ensure that the calling process identity remains consistent throughout the operation lifecycle. The incomplete flag mapping means that certain identity-related flags are not properly accounted for in the reference counting mechanism, creating a race condition where multiple processes might incorrectly reference the same memory object. This flaw particularly affects the kernel's memory management subsystem, where the use-after-free condition occurs when objects are deallocated before all references to them are properly released.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially enable privilege escalation and system instability. Attackers who can manipulate the io_uring subsystem to trigger this condition may be able to execute arbitrary code with kernel privileges, since the use-after-free vulnerability can be exploited to overwrite critical kernel data structures. The vulnerability affects all Linux kernel versions that include the affected io_uring implementation, making it particularly dangerous in production environments where kernel updates may be delayed. The inconsistent reference counting behavior also impacts system reliability, potentially causing kernel panics or unpredictable behavior during high-concurrency I/O operations.
Security researchers have identified this issue through careful analysis of the kernel's memory management and process identity handling mechanisms, with the vulnerability mapping to CWE-415: Double Free and CWE-416: Use After Free. The exploitability of this vulnerability aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, as it provides a pathway for attackers to gain elevated system privileges. The recommended mitigation strategy involves upgrading to the specific kernel commit df3f3bb5059d20ef094d6b2f0256c4bf4127a859, which corrects the incomplete flag mapping and ensures proper reference counting behavior. Organizations should also implement monitoring for suspicious io_uring operations and consider applying the patch immediately, as the vulnerability does not require user interaction to exploit and can be triggered through legitimate I/O operations.