net: shaper: rework the VALID marking (again)

Summary

In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant. The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU. Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner.

Timeline

1. Jul 19, 2026, 3:39 PM UTCCVE published
2. Oct 16, 2026, 3:35 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 19, 2026, 8:28 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 93954b40f6a4fc43226c01a15b02732f884500f1 · fixed in 2417df5e7bb4184b9d3a2988036bf2c46e594545; From 93954b40f6a4fc43226c01a15b02732f884500f1 · fixed in 96ea960dd40fd55302e0fd755176f26a95e6a50c; From 93954b40f6a4fc43226c01a15b02732f884500f1 · fixed in b8d7519352ba8c6df83259295d4a3bad093cae90

• Linux Linux

  6.13

• KernelLinux

  From 6.13.0 · fixed in 6.18.34; From 6.19.0 · fixed in 7.0.11

References 3