CVE-2026-46020

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: validate damosquotagoal->nid for nodemem{used,free}_bp

Patch series "mm/damon/core: validate damosquotagoal->nid".

nodemem[cg]{used,free}bp DAMOS quota goals receive the node id. The node id is used for simeminfonode() and NODEDATA() without proper validation. As a result, privileged users can trigger an out of bounds memory access using DAMON_SYSFS. Fix the issues.

The issue was originally reported [1] with a fix by another author. The original author announced [2] that they will stop working including the fix that was still in the review stage. Hence I'm restarting this.

This patch (of 2):

Users can set damosquotagoal->nid with arbitrary value for nodemem{used,free}bp. But DAMON core is using those for simeminfo_node() without the validation of the value. This can result in out of bounds memory access. The issue can actually triggered using DAMON user-space tool (damo), like below.

$ sudo ./damo start --damos_action stat \
    --damos_quota_goal node_mem_used_bp 50% -1 \
    --damos_quota_interval 1s
$ sudo dmesg
[...]
[   65.565986] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000098

Fix this issue by adding the validation of the given node. If an invalid node id is given, it returns 0% for used memory ratio, and 100% for free memory ratio.