CVE-2022-49890 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
capabilities: fix potential memleak on error path from vfs_getxattr_alloc()
In cap_inode_getsecurity(), we will use vfs_getxattr_alloc() to complete the memory allocation of tmpbuf, if we have completed the memory allocation of tmpbuf, but failed to call handler->get(...), there will be a memleak in below logic:
|-- ret = (int)vfs_getxattr_alloc(mnt_userns, ...) | /* ^^^ alloc for tmpbuf */ |-- value = krealloc(*xattr_value, error + 1, flags) | /* ^^^ alloc memory */ |-- error = handler->get(handler, ...) | /* error! */ |-- *xattr_value = value | /* xattr_value is &tmpbuf (memory leak!) */
So we will try to free(tmpbuf) after vfs_getxattr_alloc() fails to fix it.
[PM: subject line and backtrace tweaks]
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Analysis
by VulDB Data Team • 08/15/2025
The vulnerability described in CVE-2022-49890 represents a memory leak within the Linux kernel's capabilities implementation, specifically affecting the cap_inode_getsecurity() function. This flaw occurs during the execution of extended attribute operations when the kernel attempts to retrieve security information from inodes. The issue manifests in the interaction between vfs_getxattr_alloc() and the capability handling subsystem, where memory allocation occurs but subsequent error handling fails to properly release allocated resources. The vulnerability is classified as a memory leak under CWE-401, which specifically addresses improper memory management and resource leaks in software systems. This memory leak represents a potential denial of service vector that could gradually consume system resources over time.
The technical implementation of this vulnerability occurs within the kernel's security framework where the cap_inode_getsecurity() function orchestrates the retrieval of security capabilities associated with inodes. When vfs_getxattr_alloc() successfully allocates memory for tmpbuf through the virtual file system layer, the subsequent call to handler->get() may fail due to various error conditions such as insufficient permissions, invalid parameters, or system resource constraints. The critical flaw emerges in the error handling path where the function fails to properly release the previously allocated tmpbuf memory before the error condition is processed. The memory allocation sequence shows that while the initial allocation through vfs_getxattr_alloc() succeeds, the subsequent krealloc() operation followed by the handler->get() call may fail, leaving tmpbuf in an inconsistent state where the allocated memory is never freed. This particular memory leak occurs because the code attempts to assign the allocated value back to *xattr_value which points to tmpbuf, but the error path does not properly clean up the original allocation.
The operational impact of this vulnerability extends beyond simple memory consumption, as it represents a potential vector for resource exhaustion attacks against Linux systems. While individual memory leaks may appear trivial, in sustained attack scenarios or high-traffic environments, these cumulative memory allocations can lead to system instability, reduced performance, and potential denial of service conditions. The vulnerability affects systems running Linux kernels that implement the capabilities security framework, which is fundamental to Unix-like operating systems for implementing fine-grained access controls. The memory leak could be exploited by malicious actors who repeatedly trigger the affected code path to gradually deplete available memory resources, particularly in containerized environments or systems with limited memory resources where such leaks could have more pronounced effects. According to ATT&CK framework category T1499, this vulnerability could be leveraged as part of resource exhaustion attacks that target system stability and availability.
The fix implemented for CVE-2022-49890 addresses the memory leak by ensuring proper cleanup of allocated memory when vfs_getxattr_alloc() fails to complete the operation successfully. The solution involves adding explicit memory freeing operations after error conditions are detected in the execution path, specifically ensuring that tmpbuf memory is properly released when the handler->get() call fails. This remediation aligns with security best practices for memory management and follows the principle of least privilege by ensuring that all allocated resources are properly accounted for and released. The fix demonstrates proper error handling methodology that prevents resource leaks in kernel space operations and ensures that the kernel's memory management remains robust under error conditions. The implementation follows established patterns for kernel memory management and integrates with existing kernel subsystems that handle extended attribute operations. System administrators should apply the relevant kernel updates that contain this fix to protect against potential exploitation of this memory leak vulnerability, particularly in environments where security and system stability are paramount considerations.