CVE-2025-38493 tracing/osnoise: Fix crash in timerlat_dump_stack()
A local attacker can trigger a kernel panic in the Linux kernel's osnoise tracer by exploiting a buffer overflow in timerlat_dump_stack, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-38493?
CVE-2025-38493 is a medium-severity denial of service vulnerability in Linux kernel, published on 28 Jul 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tracing/osnoise: Fix crash in timerlat_dump_stack()
We have observed kernel panics when using timerlat with stack saving, with the following dmesg output:
memcpy: detected buffer overflow: 88 byte write of buffer size 0 WARNING: CPU: 2 PID: 8153 at lib/string_helpers.c:1032 __fortify_report+0x55/0xa0 CPU: 2 UID: 0 PID: 8153 Comm: timerlatu/2 Kdump: loaded Not tainted 6.15.3-200.fc42.x86_64 #1 PREEMPT(lazy) Call Trace: <TASK> ? trace_buffer_lock_reserve+0x2a/0x60 __fortify_panic+0xd/0xf __timerlat_dump_stack.cold+0xd/0xd timerlat_dump_stack.part.0+0x47/0x80 timerlat_fd_read+0x36d/0x390 vfs_read+0xe2/0x390 ? syscall_exit_to_user_mode+0x1d5/0x210 ksys_read+0x73/0xe0 do_syscall_64+0x7b/0x160 ? exc_page_fault+0x7e/0x1a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
__timerlat_dump_stack() constructs the ftrace stack entry like this:
struct stack_entry *entry; ... memcpy(&entry->caller, fstack->calls, size); entry->size = fstack->nr_entries;
Since commit e7186af7fb26 ("tracing: Add back FORTIFY_SOURCE logic to kernel_stack event structure"), struct stack_entry marks its caller field with __counted_by(size). At the time of the memcpy, entry->size contains garbage from the ringbuffer, which under some circumstances is zero, triggering a kernel panic by buffer overflow.
Populate the size field before the memcpy so that the out-of-bounds check knows the correct size. This is analogous to __ftrace_trace_stack().
Weakness: CWE-674
Which versions are affected by CVE-2025-38493?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38493?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-38493 being exploited?
There is no known exploitation of CVE-2025-38493 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-65946, BELL-CVE-2025-38493, DEBIAN-CVE-2025-38493, GHSA-2xmx-r7cc-9x6c, ROOT-OS-UBUNTU-2404-CVE-2025-38493, UBUNTU-CVE-2025-38493.