CVE-2025-38034
Analyzed Analyzed - Analysis Complete
BaseFortify

Publication date: 2025-06-18

Last updated on: 2025-12-17

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: correct the order of prelim_ref arguments in btrfs__prelim_ref btrfs_prelim_ref() calls the old and new reference variables in the incorrect order. This causes a NULL pointer dereference because oldref is passed as NULL to trace_btrfs_prelim_ref_insert(). Note, trace_btrfs_prelim_ref_insert() is being called with newref as oldref (and oldref as NULL) on purpose in order to print out the values of newref. To reproduce: echo 1 > /sys/kernel/debug/tracing/events/btrfs/btrfs_prelim_ref_insert/enable Perform some writeback operations. Backtrace: BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 115949067 P4D 115949067 PUD 11594a067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 1 UID: 0 PID: 1188 Comm: fsstress Not tainted 6.15.0-rc2-tester+ #47 PREEMPT(voluntary) 7ca2cef72d5e9c600f0c7718adb6462de8149622 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014 RIP: 0010:trace_event_raw_event_btrfs__prelim_ref+0x72/0x130 Code: e8 43 81 9f ff 48 85 c0 74 78 4d 85 e4 0f 84 8f 00 00 00 49 8b 94 24 c0 06 00 00 48 8b 0a 48 89 48 08 48 8b 52 08 48 89 50 10 <49> 8b 55 18 48 89 50 18 49 8b 55 20 48 89 50 20 41 0f b6 55 28 88 RSP: 0018:ffffce44820077a0 EFLAGS: 00010286 RAX: ffff8c6b403f9014 RBX: ffff8c6b55825730 RCX: 304994edf9cf506b RDX: d8b11eb7f0fdb699 RSI: ffff8c6b403f9010 RDI: ffff8c6b403f9010 RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000010 R10: 00000000ffffffff R11: 0000000000000000 R12: ffff8c6b4e8fb000 R13: 0000000000000000 R14: ffffce44820077a8 R15: ffff8c6b4abd1540 FS: 00007f4dc6813740(0000) GS:ffff8c6c1d378000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 000000010eb42000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: <TASK> prelim_ref_insert+0x1c1/0x270 find_parent_nodes+0x12a6/0x1ee0 ? __entry_text_end+0x101f06/0x101f09 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 btrfs_is_data_extent_shared+0x167/0x640 ? fiemap_process_hole+0xd0/0x2c0 extent_fiemap+0xa5c/0xbc0 ? __entry_text_end+0x101f05/0x101f09 btrfs_fiemap+0x7e/0xd0 do_vfs_ioctl+0x425/0x9d0 __x64_sys_ioctl+0x75/0xc0
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Meta Information
Published
2025-06-18
Last Modified
2025-12-17
Generated
2026-05-07
AI Q&A
2025-06-18
EPSS Evaluated
2026-05-05
NVD
CVE-2025-38034
Affected Vendors & Products
Showing 13 associated CPEs
Vendor Product Version / Range
linux linux_kernel to 5.4.294 (exc)
linux linux_kernel From 5.5 (inc) to 5.10.238 (exc)
linux linux_kernel From 5.11 (inc) to 5.15.185 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.141 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.93 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.31 (exc)
linux linux_kernel From 6.13 (inc) to 6.14.9 (exc)
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
linux linux_kernel 6.15
debian debian_linux 11.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a bug in the Linux kernel's btrfs filesystem code where the function btrfs_prelim_ref() calls its arguments in the wrong order. Specifically, the old reference variable is passed as NULL to another function, trace_btrfs_prelim_ref_insert(), which causes a NULL pointer dereference and leads to a kernel crash (Oops). This happens because the function is intentionally called with new reference as old reference and old reference as NULL to print values, but the argument order is incorrect, causing the crash during certain writeback operations.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash due to a NULL pointer dereference when performing certain writeback operations on the btrfs filesystem. This can lead to system instability, potential data loss, or denial of service as the kernel encounters an unrecoverable error and stops functioning properly.


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

This vulnerability can be detected by enabling the tracing event for btrfs_prelim_ref_insert and then performing some writeback operations to observe if a NULL pointer dereference occurs. You can enable the tracing event with the command: echo 1 > /sys/kernel/debug/tracing/events/btrfs/btrfs_prelim_ref_insert/enable. Monitoring kernel logs for BUG or Oops messages related to btrfs_prelim_ref_insert can also help detect the issue.


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