CVE-2025-39782
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-11

Last updated on: 2025-11-03

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: jbd2: prevent softlockup in jbd2_log_do_checkpoint() Both jbd2_log_do_checkpoint() and jbd2_journal_shrink_checkpoint_list() periodically release j_list_lock after processing a batch of buffers to avoid long hold times on the j_list_lock. However, since both functions contend for j_list_lock, the combined time spent waiting and processing can be significant. jbd2_journal_shrink_checkpoint_list() explicitly calls cond_resched() when need_resched() is true to avoid softlockups during prolonged operations. But jbd2_log_do_checkpoint() only exits its loop when need_resched() is true, relying on potentially sleeping functions like __flush_batch() or wait_on_buffer() to trigger rescheduling. If those functions do not sleep, the kernel may hit a softlockup. watchdog: BUG: soft lockup - CPU#3 stuck for 156s! [kworker/u129:2:373] CPU: 3 PID: 373 Comm: kworker/u129:2 Kdump: loaded Not tainted 6.6.0+ #10 Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.27 06/13/2017 Workqueue: writeback wb_workfn (flush-7:2) pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : native_queued_spin_lock_slowpath+0x358/0x418 lr : jbd2_log_do_checkpoint+0x31c/0x438 [jbd2] Call trace: native_queued_spin_lock_slowpath+0x358/0x418 jbd2_log_do_checkpoint+0x31c/0x438 [jbd2] __jbd2_log_wait_for_space+0xfc/0x2f8 [jbd2] add_transaction_credits+0x3bc/0x418 [jbd2] start_this_handle+0xf8/0x560 [jbd2] jbd2__journal_start+0x118/0x228 [jbd2] __ext4_journal_start_sb+0x110/0x188 [ext4] ext4_do_writepages+0x3dc/0x740 [ext4] ext4_writepages+0xa4/0x190 [ext4] do_writepages+0x94/0x228 __writeback_single_inode+0x48/0x318 writeback_sb_inodes+0x204/0x590 __writeback_inodes_wb+0x54/0xf8 wb_writeback+0x2cc/0x3d8 wb_do_writeback+0x2e0/0x2f8 wb_workfn+0x80/0x2a8 process_one_work+0x178/0x3e8 worker_thread+0x234/0x3b8 kthread+0xf0/0x108 ret_from_fork+0x10/0x20 So explicitly call cond_resched() in jbd2_log_do_checkpoint() to avoid softlockup.
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Meta Information
Published
2025-09-11
Last Modified
2025-11-03
Generated
2026-05-07
AI Q&A
2025-09-11
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39782
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
linux kernel 5.10.244-1
linux kernel 6.1.153-1
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 potential softlockup in the Linux kernel's jbd2 subsystem, specifically in the jbd2_log_do_checkpoint() function. The issue arises because this function does not explicitly call cond_resched() to yield the CPU during long operations, relying instead on other functions that may or may not sleep. If those functions do not sleep, the kernel can become stuck in a softlockup, where the CPU is busy but not making progress, causing system responsiveness issues.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to experience a softlockup, where a CPU core becomes stuck for an extended period (e.g., over 150 seconds) during journal checkpoint operations. This can lead to system unresponsiveness, degraded performance, or potential system hangs, impacting the stability and reliability of systems running affected kernel versions.


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

This vulnerability can be detected by monitoring for kernel soft lockup warnings related to jbd2_log_do_checkpoint(). You can check the system logs for messages like 'watchdog: BUG: soft lockup' involving jbd2 functions. For example, use commands such as 'dmesg | grep -i softlockup' or 'journalctl -k | grep jbd2' to find relevant kernel messages indicating the issue.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where jbd2_log_do_checkpoint() explicitly calls cond_resched() to prevent softlockups. Until an update is applied, monitoring for soft lockup warnings and minimizing heavy writeback workloads may reduce the chance of encountering the issue.


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