CVE-2024-50087 in Linux
Summary
by MITRE • 10/29/2024
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix uninitialized pointer free on read_alloc_one_name() error
The function read_alloc_one_name() does not initialize the name field of the passed fscrypt_str struct if kmalloc fails to allocate the corresponding buffer. Thus, it is not guaranteed that fscrypt_str.name is initialized when freeing it.
This is a follow-up to the linked patch that fixes the remaining instances of the bug introduced by commit e43eec81c516 ("btrfs: use struct qstr instead of name and namelen pairs").
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2024-50087 represents a critical memory management flaw within the Linux kernel's btrfs filesystem implementation. This issue specifically affects the read_alloc_one_name() function which handles the allocation and processing of cryptographic string structures during filesystem operations. The flaw stems from improper initialization of memory structures that can lead to unpredictable behavior and potential security implications. The vulnerability was introduced by a previous commit e43eec81c516 that modified how btrfs handles name resolution by replacing traditional name and namelen pairs with struct qstr structures, creating a regression in error handling procedures.
The technical core of this vulnerability lies in the function's failure to properly initialize the name field of the fscrypt_str structure when memory allocation fails. When kmalloc encounters an allocation failure during the read_alloc_one_name() operation, the function continues execution without setting the name field to a valid state. This creates a scenario where subsequent memory freeing operations may attempt to dereference uninitialized pointers, potentially leading to memory corruption or information disclosure. The flaw exists in the error path handling where the function assumes proper initialization has occurred even when allocation failures occur. According to CWE-457, this represents a use of uninitialized variable, while the improper handling of memory allocation failures aligns with CWE-758, indicating a weakness in resource management.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially be exploited to gain unauthorized access to filesystem data or compromise system stability. When the btrfs filesystem encounters certain error conditions during name resolution operations, particularly those involving cryptographic string handling, the uninitialized pointer dereference can cause the kernel to behave unpredictably. This could manifest as system crashes, data corruption, or in more severe cases, privilege escalation opportunities that align with ATT&CK technique T1068, which covers privilege escalation through local exploits. The vulnerability affects systems running Linux kernels with btrfs filesystem support, particularly those utilizing encryption features where fscrypt_str structures are actively used.
Mitigation strategies for CVE-2024-50087 require immediate kernel updates to address the memory initialization issue. System administrators should prioritize patching affected systems to ensure the proper initialization of fscrypt_str structures during error conditions. The fix implemented in the kernel resolves the uninitialized pointer issue by ensuring that the name field is properly initialized even when allocation fails, preventing subsequent memory operations from encountering invalid pointer states. Additionally, monitoring for kernel panic events or filesystem corruption reports can help identify potential exploitation attempts. Organizations should also implement routine system audits to verify proper kernel versions are deployed and maintain updated security configurations for btrfs filesystems, particularly those utilizing encryption features. The fix addresses the root cause by ensuring proper error handling pathways maintain consistent memory state throughout the function execution lifecycle, preventing the uninitialized variable scenario that could lead to exploitable conditions.