dma-buf: dma-fence: Fix potential NULL pointer dereference
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: dma-buf: dma-fence: Fix potential NULL pointer dereference The commit mentioned in the fixes tag below introduced a mechanism through which fence producers can fully decouple from fence consumers. This, desirable, mechanism is based on the fence's signaled-bit as the "decoupling point". A sophisticated interaction between RCU and atomic instructions attempts to ensure that fence consumers can still interact with fence producers through the dma_fence_ops (callback pointers into the producer). This is the desired behavior: to check for decoupling, the signaled-bit is first checked. If it's not yet signaled, RCU ensures that the ops pointer cannot yet be NULL. Hereby, dma_fence_signal_timestamp_locked() first sets the signaled-bit, and then sets the ops pointer to NULL. Readers first load the ops pointer, and then check through the signaled-bit whether the pointer can legally be accessed. These set and load operations could occur out of order on weakly ordered platforms. This problem can be solved very elegantly by using the ops pointer itself as the synchronization point. The pointer is either NULL, or cannot become NULL while it is being used thanks to RCU. Replace the signaled-bit check in dma_fence_timeline_name() and dma_fence_driver_name().
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
Version range not reported
- Linux Linux
7.1