CVE-2023-53783 blk-iocost: fix divide by 0 error in calc_lcoefs()
A local attacker with high privileges can cause a kernel crash by writing specific values to the cgroup io.cost.model file, resulting in a denial of service.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53783?
CVE-2023-53783 is a denial of service vulnerability in Linux, published on 9 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
blk-iocost: fix divide by 0 error in calc_lcoefs()
echo max of u64 to cost.model can cause divide by 0 error.
# echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model
divide error: 0000 [#1] PREEMPT SMP RIP: 0010:calc_lcoefs+0x4c/0xc0 Call Trace: <TASK> ioc_refresh_params+0x2b3/0x4f0 ioc_cost_model_write+0x3cb/0x4c0 ? _copy_from_iter+0x6d/0x6c0 ? kernfs_fop_write_iter+0xfc/0x270 cgroup_file_write+0xa0/0x200 kernfs_fop_write_iter+0x17d/0x270 vfs_write+0x414/0x620 ksys_write+0x73/0x160 __x64_sys_write+0x1e/0x30 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL, overflow would happen if bps plus IOC_PAGE_SIZE is greater than ULLONG_MAX, it can cause divide by 0 error.
Fix the problem by setting basecost
Which versions are affected by CVE-2023-53783?
How do I fix CVE-2023-53783?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2023-53783 being exploited?
There is no known exploitation of CVE-2023-53783 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-53783, DEBIAN-CVE-2023-53783, GHSA-6wcv-9326-m4qg, UBUNTU-CVE-2023-53783.