CVE-2025-39683

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

tracing: Limit access to parser->buffer when trace_get_user failed

When the length of the string written to set_ftrace_filter exceeds

FTRACE_BUFF_MAX, the following KASAN alarm will be triggered:

BUG: KASAN: slab-out-of-bounds in strsep+0x18c/0x1b0

Read of size 1 at addr ffff0000d00bd5ba by task ash/165

CPU: 1 UID: 0 PID: 165 Comm: ash Not tainted 6.16.0-g6bcdbd62bd56-dirty

Hardware name: linux,dummy-virt (DT)

Call trace:

show_stack+0x34/0x50 (C)

dump_stack_lvl+0xa0/0x158

print_address_description.constprop.0+0x88/0x398

print_report+0xb0/0x280

kasan_report+0xa4/0xf0

__asan_report_load1_noabort+0x20/0x30

strsep+0x18c/0x1b0

ftrace_process_regex.isra.0+0x100/0x2d8

ftrace_regex_release+0x484/0x618

__fput+0x364/0xa58

____fput+0x28/0x40

task_work_run+0x154/0x278

do_notify_resume+0x1f0/0x220

el0_svc+0xec/0xf0

el0t_64_sync_handler+0xa0/0xe8

el0t_64_sync+0x1ac/0x1b0

The reason is that trace_get_user will fail when processing a string

longer than FTRACE_BUFF_MAX, but not set the end of parser->buffer to 0.

Then an OOB access will be triggered in ftrace_regex_release->

ftrace_process_regex->strsep->strpbrk. We can solve this problem by

limiting access to parser->buffer when trace_get_user failed.