CVE-2024-39481 in Linux
Summary
by MITRE • 07/05/2024
In the Linux kernel, the following vulnerability has been resolved:
media: mc: Fix graph walk in media_pipeline_start
The graph walk tries to follow all links, even if they are not between pads. This causes a crash with, e.g. a MEDIA_LNK_FL_ANCILLARY_LINK link.
Fix this by allowing the walk to proceed only for MEDIA_LNK_FL_DATA_LINK links.
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Analysis
by VulDB Data Team • 07/08/2024
The vulnerability identified as CVE-2024-39481 resides within the Linux kernel's media subsystem, specifically affecting the media pipeline framework responsible for managing multimedia data flows through complex graph structures. This flaw manifests in the media_pipeline_start function where the graph traversal mechanism attempts to process all available links regardless of their type or purpose within the media graph topology. The issue occurs when the kernel's media infrastructure encounters ancillary links that are not intended for data flow processing, leading to unpredictable behavior and system instability.
The technical implementation flaw stems from an insufficient link type validation mechanism during graph traversal operations. When the media pipeline walker processes connections between media entities, it indiscriminately follows every link present in the graph structure without proper filtering based on link characteristics. This oversight becomes particularly problematic when encountering MEDIA_LNK_FL_ANCILLARY_LINK types which serve metadata or control purposes rather than actual data transmission paths. The kernel's graph walking algorithm fails to distinguish between data links that should be processed and ancillary links that should be ignored during pipeline initialization.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the stability of multimedia applications and kernel subsystems. When the media pipeline initialization process encounters malformed or unexpected link configurations, the kernel may experience memory corruption or null pointer dereferences that can lead to complete system crashes or denial of service conditions. This vulnerability affects any system utilizing the Linux kernel's media framework for video capture, processing, or streaming operations, particularly those involving complex media graph topologies with mixed link types.
The fix implemented addresses the core issue by introducing a link type filter that restricts graph traversal to only MEDIA_LNK_FL_DATA_LINK types during pipeline start operations. This approach aligns with established security practices for graph traversal and access control mechanisms. The solution prevents the kernel from attempting to process ancillary or control links as if they were data transmission paths, thereby eliminating the crash conditions while maintaining proper functionality for legitimate data flow operations. This remediation follows best practices for kernel security and aligns with the principle of least privilege in system design. The fix has been incorporated into the media subsystem's graph walking logic to ensure that only appropriate link types are processed during media pipeline initialization, reducing the attack surface and preventing potential exploitation scenarios that could lead to privilege escalation or system compromise.