In the Linux kernel, the following vulnerability has been resolved: samples/damon/mtier: error out for zero quota goal target values Patch

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 damos_quota_score()".

DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division
by zero in damos_quota_score(). Avoid it by adding parameters validation
checks.

This patch (of 2):

damos_quota_score() can trigger division by zero if the target_value is
zero. DAMON_SAMPLE_MTIER lets users set the target_value via
node0_mem_{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
node0_mem{used,free}_bp parameter values.

DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite
bad. Also the zero node0_mem_free_bp 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:

 1# cd /sys/module/damon_sample_mtier/parameters
 2# echo 4096 > node0_start_addr
 3# echo 8192 > node0_end_addr
 4# echo 8192 > node1_start_addr
 5# echo 81920 > node1_end_addr
 6# echo 0 > node0_mem_free_bp
 7# echo Y > enabled
 8# dmesg -w
 9[...]
10[18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI
11[...]
12[18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480
13[...]

This issue was discovered [1] by Sashiko.