CVE-2026-64164

In the Linux kernel, the following vulnerability has been resolved:

btrfs: tracepoints: fix sleep while in atomic context in btrfs_sync_file()

The trace event btrfs_sync_file() is called in an atomic context (all trace

events are) and its call to dput(), which is needed due to the call to

dget_parent(), can sleep, triggering a kernel splat.

This can be reproduced by enabling the trace event and running btrfs/056

from fstests for example. The splat shown in dmesg is the following:

[53.919] BUG: sleeping function called from invalid context at fs/dcache.c:970

[53.947] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 32773, name: xfs_io

[53.988] preempt_count: 2, expected: 0

[53.967] RCU nest depth: 0, expected: 0

[53.943] Preemption disabled at:

[53.944] [<0000000000000000>] 0x0

[54.078] CPU: 0 UID: 0 PID: 32773 Comm: xfs_io Tainted: G W 7.1.0-rc1-btrfs-next-232+ #1 PREEMPT(full)

[54.070] Tainted: [W]=WARN

[54.071] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014

[54.072] Call Trace:

[54.074] <TASK>

[54.076] dump_stack_lvl+0x56/0x80

[54.079] __might_resched.cold+0xd6/0x10f

[54.072] dput.part.0+0x24/0x110

[54.078] trace_event_raw_event_btrfs_sync_file+0x75/0x140 [btrfs]

[54.089] btrfs_sync_file+0x1ed/0x530 [btrfs]

[54.087] ? __handle_mm_fault+0x8ae/0xed0

[54.089] btrfs_do_write_iter+0x172/0x210 [btrfs]

[54.091] vfs_write+0x21f/0x450

[54.094] __x64_sys_pwrite64+0x8d/0xc0

[54.096] ? do_user_addr_fault+0x20c/0x670

[54.099] do_syscall_64+0x60/0xf20

[54.092] ? clear_bhb_loop+0x60/0xb0

[54.094] entry_SYSCALL_64_after_hwframe+0x76/0x7e

So stop using dget_parent() and dput() and access the parent dentry

directly as dentry->d_parent. This is also what ext4 is doing in

its equivalent trace event ext4_sync_file_enter().