CVE-2025-38269 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
btrfs: exit after state insertion failure at btrfs_convert_extent_bit()
If insert_state() state failed it returns an error pointer and we call extent_io_tree_panic() which will trigger a BUG() call. However if CONFIG_BUG is disabled, which is an uncommon and exotic scenario, then we fallthrough and call cache_state() which will dereference the error pointer, resulting in an invalid memory access.
So jump to the 'out' label after calling extent_io_tree_panic(), it also makes the code more clear besides dealing with the exotic scenario where CONFIG_BUG is disabled.
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2025-38269 resides within the Linux kernel's btrfs file system implementation, specifically in the btrfs_convert_extent_bit() function. This flaw represents a critical memory safety issue that can lead to system instability and potential privilege escalation. The vulnerability manifests when the insert_state() function fails during state insertion operations, creating a scenario where error handling becomes problematic due to conditional compilation directives. The btrfs file system, designed for enterprise storage solutions, is widely deployed across servers and storage arrays where reliability and stability are paramount. When the kernel encounters a state insertion failure, the normal error handling path should prevent further execution, but the current implementation contains a logic flaw that allows execution to continue under certain conditions.
The technical flaw occurs in the error handling mechanism of the btrfs subsystem where the extent_io_tree_panic() function is called upon state insertion failure. This function typically triggers a kernel BUG() call that halts execution, but in configurations where CONFIG_BUG is disabled, the system does not enter the panic state as expected. Instead, execution continues to the cache_state() function where it attempts to dereference the error pointer returned by insert_state(), resulting in invalid memory access and potential system crashes. This represents a classic null pointer dereference vulnerability that can be exploited to cause denial of service or potentially gain unauthorized access to system resources. The flaw is particularly concerning because it operates in an uncommon but valid kernel configuration, making it difficult to detect during routine testing and development phases.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the integrity of storage operations within btrfs file systems. Systems relying on btrfs for critical data storage, including database servers, cloud infrastructure, and enterprise storage solutions, could experience unexpected downtime or data corruption when this vulnerability is triggered. The vulnerability affects systems where the kernel is compiled with CONFIG_BUG disabled, which while uncommon, represents a valid configuration option that may be used in specialized environments or for debugging purposes. Attackers could potentially exploit this vulnerability to cause system instability, leading to denial of service conditions that could affect availability of critical services. The vulnerability aligns with CWE-476 which describes null pointer dereference conditions, and could be mapped to ATT&CK technique T1490 for data destruction and system instability.
Mitigation strategies for this vulnerability primarily involve applying the kernel patch that modifies the btrfs_convert_extent_bit() function to properly handle error conditions by jumping to the 'out' label immediately after calling extent_io_tree_panic(). This ensures that execution does not continue to cache_state() when an error has occurred, preventing the invalid memory access. System administrators should prioritize updating their kernel versions to include this fix, particularly in production environments where btrfs file systems are deployed. Organizations should also implement monitoring to detect potential exploitation attempts and maintain robust backup and recovery procedures to mitigate the impact of system crashes. The fix addresses the root cause by ensuring proper error handling flow control, making the code more resilient to edge cases and reducing the attack surface for potential exploitation.