CVE-2023-54242
Unknown Unknown - Not Provided
Division by Zero Vulnerability in Linux Kernel BFQ Block Scheduler

Publication date: 2025-12-30

Last updated on: 2025-12-30

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: block, bfq: Fix division by zero error on zero wsum When the weighted sum is zero the calculation of limit causes a division by zero error. Fix this by continuing to the next level. This was discovered by running as root: stress-ng --ioprio 0 Fixes divison by error oops: [ 521.450556] divide error: 0000 [#1] SMP NOPTI [ 521.450766] CPU: 2 PID: 2684464 Comm: stress-ng-iopri Not tainted 6.2.1-1280.native #1 [ 521.451117] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014 [ 521.451627] RIP: 0010:bfqq_request_over_limit+0x207/0x400 [ 521.451875] Code: 01 48 8d 0c c8 74 0b 48 8b 82 98 00 00 00 48 8d 0c c8 8b 85 34 ff ff ff 48 89 ca 41 0f af 41 50 48 d1 ea 48 98 48 01 d0 31 d2 <48> f7 f1 41 39 41 48 89 85 34 ff ff ff 0f 8c 7b 01 00 00 49 8b 44 [ 521.452699] RSP: 0018:ffffb1af84eb3948 EFLAGS: 00010046 [ 521.452938] RAX: 000000000000003c RBX: 0000000000000000 RCX: 0000000000000000 [ 521.453262] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffb1af84eb3978 [ 521.453584] RBP: ffffb1af84eb3a30 R08: 0000000000000001 R09: ffff8f88ab8a4ba0 [ 521.453905] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8f88ab8a4b18 [ 521.454224] R13: ffff8f8699093000 R14: 0000000000000001 R15: ffffb1af84eb3970 [ 521.454549] FS: 00005640b6b0b580(0000) GS:ffff8f88b3880000(0000) knlGS:0000000000000000 [ 521.454912] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 521.455170] CR2: 00007ffcbcae4e38 CR3: 00000002e46de001 CR4: 0000000000770ee0 [ 521.455491] PKRU: 55555554 [ 521.455619] Call Trace: [ 521.455736] <TASK> [ 521.455837] ? bfq_request_merge+0x3a/0xc0 [ 521.456027] ? elv_merge+0x115/0x140 [ 521.456191] bfq_limit_depth+0xc8/0x240 [ 521.456366] __blk_mq_alloc_requests+0x21a/0x2c0 [ 521.456577] blk_mq_submit_bio+0x23c/0x6c0 [ 521.456766] __submit_bio+0xb8/0x140 [ 521.457236] submit_bio_noacct_nocheck+0x212/0x300 [ 521.457748] submit_bio_noacct+0x1a6/0x580 [ 521.458220] submit_bio+0x43/0x80 [ 521.458660] ext4_io_submit+0x23/0x80 [ 521.459116] ext4_do_writepages+0x40a/0xd00 [ 521.459596] ext4_writepages+0x65/0x100 [ 521.460050] do_writepages+0xb7/0x1c0 [ 521.460492] __filemap_fdatawrite_range+0xa6/0x100 [ 521.460979] file_write_and_wait_range+0xbf/0x140 [ 521.461452] ext4_sync_file+0x105/0x340 [ 521.461882] __x64_sys_fsync+0x67/0x100 [ 521.462305] ? syscall_exit_to_user_mode+0x2c/0x1c0 [ 521.462768] do_syscall_64+0x3b/0xc0 [ 521.463165] entry_SYSCALL_64_after_hwframe+0x5a/0xc4 [ 521.463621] RIP: 0033:0x5640b6c56590 [ 521.464006] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 80 3d 71 70 0e 00 00 74 17 b8 4a 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c
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Meta Information
Published
2025-12-30
Last Modified
2025-12-30
Generated
2026-05-06
AI Q&A
2025-12-30
EPSS Evaluated
2026-05-05
NVD
CVE-2023-54242
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.2.1
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a division by zero error in the Linux kernel's block layer, specifically in the bfq (Budget Fair Queueing) scheduler. When the weighted sum (wsum) is zero, the calculation of a limit causes a division by zero, leading to a kernel crash (oops). The issue occurs during I/O priority stress testing and has been fixed by skipping the problematic calculation when wsum is zero.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash due to a division by zero error, potentially leading to system instability or denial of service. It can disrupt normal system operations, especially under certain I/O priority stress conditions, affecting availability.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by observing kernel logs for division by zero errors related to bfq (Budget Fair Queueing) block scheduler. Specifically, look for kernel oops messages similar to 'divide error' or stack traces involving 'bfqq_request_over_limit'. Running the command 'dmesg | grep -i divide' or 'journalctl -k | grep -i divide' may help identify such errors. Additionally, running the stress test command 'stress-ng --ioprio 0' as root can reproduce the issue if the system is vulnerable.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where this division by zero error in the bfq block scheduler is fixed. Avoid running the 'stress-ng --ioprio 0' test or similar I/O priority stress tests until the kernel is patched. Monitoring kernel logs for related errors and applying vendor-provided kernel updates is recommended.


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