CVE-2022-49853 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
net: macvlan: fix memory leaks of macvlan_common_newlink
kmemleak reports memory leaks in macvlan_common_newlink, as follows:
ip link add link eth0 name .. type macvlan mode source macaddr add
kmemleak reports:
unreferenced object 0xffff8880109bb140 (size 64): comm "ip", pid 284, jiffies 4294986150 (age 430.108s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 b8 aa 5a 12 80 88 ff ff ..........Z..... 80 1b fa 0d 80 88 ff ff 1e ff ac af c7 c1 6b 6b ..............kk backtrace: [] kmem_cache_alloc_trace+0x1c7/0x300
[] macvlan_hash_add_source+0x45/0xc0
[] macvlan_changelink_sources+0xd7/0x170
[] macvlan_common_newlink+0x38c/0x5a0
[] macvlan_newlink+0xe/0x20
[] __rtnl_newlink+0x7af/0xa50
[] rtnl_newlink+0x48/0x70
...
In the scenario where the macvlan mode is configured as 'source', macvlan_changelink_sources() will be execured to reconfigure list of remote source mac addresses, at the same time, if register_netdevice() return an error, the resource generated by macvlan_changelink_sources() is not cleaned up.
Using this patch, in the case of an error, it will execute macvlan_flush_sources() to ensure that the resource is cleaned up.
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Analysis
by VulDB Data Team • 06/28/2025
The vulnerability identified as CVE-2022-49853 represents a memory leak in the Linux kernel's macvlan network driver implementation. This issue specifically affects the macvlan_common_newlink function which handles the creation and configuration of macvlan network interfaces. The vulnerability arises from inadequate resource cleanup when certain error conditions occur during the interface setup process, creating persistent memory leaks that can accumulate over time and potentially impact system stability. The problem manifests when configuring macvlan interfaces with the 'source' mode, where the kernel attempts to manage a list of remote source MAC addresses. The kmemleak subsystem, which monitors for memory leaks in the kernel, has identified unreferenced memory objects of 64 bytes in size that remain allocated after the interface creation process fails.
The technical flaw occurs within the macvlan_changelink_sources() function which is responsible for reconfiguring the list of remote source MAC addresses when the macvlan mode is set to 'source'. During this process, if the register_netdevice() function returns an error, the resources that were allocated and processed by macvlan_changelink_sources() are not properly released. This failure to clean up allocated memory occurs because the error handling path does not invoke the appropriate cleanup mechanism. The memory leak is particularly concerning as it represents a direct violation of memory management best practices in kernel space operations, where all allocated resources must be properly freed regardless of execution path outcomes. The backtrace from kmemleak shows the memory allocation occurring through the kmem_cache_alloc_trace function, followed by the macvlan_hash_add_source function, and ultimately the macvlan_common_newlink function where the error condition triggers the leak.
The operational impact of this vulnerability extends beyond simple memory consumption as it represents a potential denial of service vector. While individual memory leaks may seem minor, in systems with high network interface creation and destruction activity, these leaks can accumulate to consume significant amounts of kernel memory. This can lead to reduced system performance, increased memory pressure, and potentially system instability or crashes. The vulnerability affects systems running Linux kernel versions where the macvlan driver is active and where macvlan interfaces are configured with source mode, which is commonly used in container networking and virtualization environments. Network administrators and system operators may observe gradual degradation in system performance over time as these memory leaks accumulate, particularly in environments with frequent network interface provisioning and deprovisioning operations.
The patch addressing this vulnerability implements a corrective mechanism that ensures proper resource cleanup when errors occur during the macvlan interface creation process. Specifically, the fix introduces a call to macvlan_flush_sources() function when error conditions are detected, ensuring that all resources allocated by macvlan_changelink_sources() are properly released. This approach aligns with established kernel development practices and security principles that mandate proper resource management in all code paths, including error handling scenarios. The solution follows the principle of least privilege and resource accountability, ensuring that kernel memory allocations are always paired with corresponding deallocations. This remediation addresses the underlying issue classified under CWE-404, which deals with improper resource release or unmanaged resource consumption, and provides protection against potential exploitation that could leverage memory exhaustion for denial of service attacks. The fix demonstrates proper error handling patterns consistent with the ATT&CK framework's emphasis on system resource management and kernel stability, ensuring that network interface operations maintain system integrity even when failures occur.