CVE-2026-74643: samples/damon/mtier: error out for zero quota goal target values
In the Linux kernel, the following vulnerability has been resolved:
samples/damon/mtier: error out for zero quota goal target values
Patch series "mm/damon: avoid division by zero from damosquotascore()".
DAMONSAMPLEMTIER and DAMONLRUSORT allow the user to trigger division by zero in damosquotascore(). Avoid it by adding parameters validation checks.
This patch (of 2):
damosquotascore() can trigger division by zero if the targetvalue is zero. DAMONSAMPLEMTIER lets users set the targetvalue via node0mem{used,free}bp parameters. It doesn't guard zero value case, though. As a result, users can trigger division by zero. Fix the issue by returning an error when the user tries to start DAMON with zero node0mem{used,free}bp parameter values.
DAMONSAMPLEMTIER is just a sample module, but the consequence is quite bad. Also the zero node0memfreebp parameter might look like a reasonable setup to some users. Hence, the issue might really happen in the real world.
One reliable way to reproduce the issue is like below:
# cd /sys/module/damonsamplemtier/parameters # echo 4096 > node0startaddr # echo 8192 > node0endaddr # echo 8192 > node1startaddr # echo 81920 > node1endaddr # echo 0 > node0memfreebp # echo Y > enabled # dmesg -w [...] [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI [...] [18792.242787] RIP: 0010:damosquotascore+0x6f/0x480 [...]
This issue was discovered [1] by Sashiko.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch mm/damon: avoid division by zero from damos_quota_score() - Configuration
Avoid setting node0_mem_free_bp to 0. The material notes this can lead to division by zero in damos_quota_score() when users provide zero quota goal target values.
DAMON_SAMPLE_MTIER (kernel module / sysfs parameters) node0_mem_free_bp (quota target/value) = non-zero - Configuration
Avoid providing zero values for the DAMON quota-related parameters node0_mem_{used,free}_bp and the corresponding node1 parameters, since damos_quota_score() can divide by zero when target_value derives from node0_mem_{used,free}_bp parameter values.
DAMON_SAMPLE_MTIER (kernel module / sysfs parameters) node0_mem_used_bp and node1_mem_{used,free}_bp (quota target/value) = non-zero