In the Linux kernel, the following vulnerability has been resolved: dm thin: make get_first_thin use rcu-safe list first function The documentation in rculist.h explains the absence of list_empty_rcu() and cautions programmers against relying on a list_empty() -> list_first() sequence in RCU safe code. This is because each of these functions performs its own READ_ONCE() of the list head. This can lead to a situation where the list_empty() sees a valid list entry, but the subsequent list_first() sees a different view of list head state after a modification. In the case of dm-thin, this author had a production box crash from a GP fault in the process_deferred_bios path. This function saw a valid list head in get_first_thin() but when it subsequently dereferenced that and turned it into a thin_c, it got the inside of the struct pool, since the list was now empty and referring to itself. The kernel on which this occurred printed both a warning about a refcount_t being saturated, and a UBSAN error for an out-of-bounds cpuid access in the queued spinlock, prior to the fault itself. When the resulting kdump was examined, it was possible to see another thread patiently waiting in thin_dtr\'s synchronize_rcu. The thin_dtr call managed to pull the thin_c out of the active thins list (and have it be the last entry in the active_thins list) at just the wrong moment which lead to this crash. Fortunately, the fix here is straight forward. Switch get_first_thin() function to use list_first_or_null_rcu() which performs just a single READ_ONCE() and returns NULL if the list is already empty. This was run against the devicemapper test suite\'s thin-provisioning suites for delete and suspend and no regressions were observed.
Find out more about CVE-2025-21664 from the MITRE-CVE dictionary and NIST NVD
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| Product Name | Status | Defect | Fixed | Downloads |
|---|---|---|---|---|
| Linux | ||||
| Wind River Linux LTS 17 | Requires LTSS | -- | -- | -- |
| Wind River Linux 8 | Requires LTSS | -- | -- | -- |
| Wind River Linux 9 | Requires LTSS | -- | -- | -- |
| Wind River Linux 7 | Requires LTSS | -- | -- | -- |
| Wind River Linux LTS 21 | Investigating | -- | -- | -- |
| Wind River Linux LTS 22 | Investigating | -- | -- | -- |
| Wind River Linux LTS 18 | Requires LTSS | -- | -- | -- |
| Wind River Linux LTS 19 | Requires LTSS | -- | -- | -- |
| Wind River Linux CD release | N/A | -- | -- | -- |
| Wind River Linux 6 | Requires LTSS | -- | -- | -- |
| Wind River Linux LTS 23 | Fixed | -- | None | -- |
| Wind River Linux LTS 24 | Fixed | -- | None | -- |
| VxWorks | ||||
| VxWorks 7 | Not Vulnerable | -- | -- | -- |
| VxWorks 6.9 | Not Vulnerable | -- | -- | -- |
| Helix Virtualization Platform Cert Edition | ||||
| Helix Virtualization Platform Cert Edition | Not Vulnerable | -- | -- | -- |
| eLxr | ||||
| eLxr 12 | Vulnerable | -- | -- | -- |
| Wind River Studio Cloud Platform | ||||
| Product Name | Status | Defect | Fixed | Downloads |
|---|
