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a16fd3ad9d
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:
# cd /sys/module/damon_sample_mtier/parameters
# echo 4096 > node0_start_addr
# echo 8192 > node0_end_addr
# echo 8192 > node1_start_addr
# echo 81920 > node1_end_addr
# echo 0 > node0_mem_free_bp
# echo Y > enabled
# dmesg -w
[...]
[18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI
[...]
[18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480
[...]
This issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260803134034.15217-1-sj@kernel.org
Link: https://lore.kernel.org/20260803134034.15217-2-sj@kernel.org
Link: https://lore.kernel.org/20260801202657.117135-1-sj@kernel.org [1]
Fixes:
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| .. | ||
| acrn | ||
| auxdisplay | ||
| binderfs | ||
| bpf | ||
| cgroup | ||
| check-exec | ||
| configfs | ||
| connector | ||
| coresight | ||
| damon | ||
| fanotify | ||
| fprobe | ||
| ftrace | ||
| hid | ||
| hidraw | ||
| hung_task | ||
| hw_breakpoint | ||
| kdb | ||
| kfifo | ||
| kmemleak | ||
| kobject | ||
| kprobes | ||
| landlock | ||
| livepatch | ||
| mei | ||
| nitro_enclaves | ||
| pfsm | ||
| pidfd | ||
| pktgen | ||
| qmi | ||
| rpmsg | ||
| rust | ||
| seccomp | ||
| timers | ||
| trace_events | ||
| trace_printk | ||
| tsm-mr | ||
| uhid | ||
| user_events | ||
| v4l | ||
| vfio-mdev | ||
| vfs | ||
| watch_queue | ||
| watchdog | ||
| workqueue/stall_detector | ||
| Kconfig | ||
| Makefile | ||