CVE-2025-38034

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: correct the order of prelim_ref arguments in btrfs__prelim_ref<br /> <br /> btrfs_prelim_ref() calls the old and new reference variables in the<br /> incorrect order. This causes a NULL pointer dereference because oldref<br /> is passed as NULL to trace_btrfs_prelim_ref_insert().<br /> <br /> Note, trace_btrfs_prelim_ref_insert() is being called with newref as<br /> oldref (and oldref as NULL) on purpose in order to print out<br /> the values of newref.<br /> <br /> To reproduce:<br /> echo 1 &gt; /sys/kernel/debug/tracing/events/btrfs/btrfs_prelim_ref_insert/enable<br /> <br /> Perform some writeback operations.<br /> <br /> Backtrace:<br /> BUG: kernel NULL pointer dereference, address: 0000000000000018<br /> #PF: supervisor read access in kernel mode<br /> #PF: error_code(0x0000) - not-present page<br /> PGD 115949067 P4D 115949067 PUD 11594a067 PMD 0<br /> Oops: Oops: 0000 [#1] SMP NOPTI<br /> CPU: 1 UID: 0 PID: 1188 Comm: fsstress Not tainted 6.15.0-rc2-tester+ #47 PREEMPT(voluntary) 7ca2cef72d5e9c600f0c7718adb6462de8149622<br /> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014<br /> RIP: 0010:trace_event_raw_event_btrfs__prelim_ref+0x72/0x130<br /> 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 8b 55 18 48 89 50 18 49 8b 55 20 48 89 50 20 41 0f b6 55 28 88<br /> RSP: 0018:ffffce44820077a0 EFLAGS: 00010286<br /> RAX: ffff8c6b403f9014 RBX: ffff8c6b55825730 RCX: 304994edf9cf506b<br /> RDX: d8b11eb7f0fdb699 RSI: ffff8c6b403f9010 RDI: ffff8c6b403f9010<br /> RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000010<br /> R10: 00000000ffffffff R11: 0000000000000000 R12: ffff8c6b4e8fb000<br /> R13: 0000000000000000 R14: ffffce44820077a8 R15: ffff8c6b4abd1540<br /> FS: 00007f4dc6813740(0000) GS:ffff8c6c1d378000(0000) knlGS:0000000000000000<br /> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> CR2: 0000000000000018 CR3: 000000010eb42000 CR4: 0000000000750ef0<br /> PKRU: 55555554<br /> Call Trace:<br /> <br /> prelim_ref_insert+0x1c1/0x270<br /> find_parent_nodes+0x12a6/0x1ee0<br /> ? __entry_text_end+0x101f06/0x101f09<br /> ? srso_alias_return_thunk+0x5/0xfbef5<br /> ? srso_alias_return_thunk+0x5/0xfbef5<br /> ? srso_alias_return_thunk+0x5/0xfbef5<br /> ? srso_alias_return_thunk+0x5/0xfbef5<br /> btrfs_is_data_extent_shared+0x167/0x640<br /> ? fiemap_process_hole+0xd0/0x2c0<br /> extent_fiemap+0xa5c/0xbc0<br /> ? __entry_text_end+0x101f05/0x101f09<br /> btrfs_fiemap+0x7e/0xd0<br /> do_vfs_ioctl+0x425/0x9d0<br /> __x64_sys_ioctl+0x75/0xc0