Description

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

tracing: Have trace_event_file have ref counters

The following can crash the kernel:

# cd /sys/kernel/tracing
# echo 'p:sched schedule' > kprobe_events
# exec 5>>events/kprobes/sched/enable
# > kprobe_events
# exec 5>&-

The above commands:

1. Change directory to the tracefs directory
2. Create a kprobe event (doesn't matter what one)
3. Open bash file descriptor 5 on the enable file of the kprobe event
4. Delete the kprobe event (removes the files too)
5. Close the bash file descriptor 5

The above causes a crash!

BUG: kernel NULL pointer dereference, address: 0000000000000028
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 6 PID: 877 Comm: bash Not tainted 6.5.0-rc4-test-00008-g2c6b6b1029d4-dirty #186
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:tracing_release_file_tr+0xc/0x50

What happens here is that the kprobe event creates a trace_event_file
"file" descriptor that represents the file in tracefs to the event. It
maintains state of the event (is it enabled for the given instance?).
Opening the "enable" file gets a reference to the event "file" descriptor
via the open file descriptor. When the kprobe event is deleted, the file is
also deleted from the tracefs system which also frees the event "file"
descriptor.

But as the tracefs file is...

Classification

CVE ID: CVE-2023-52879

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.08% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

https://git.kernel.org/stable/c/961c4511c7578d6b8f39118be919016ec3db1c1e
https://git.kernel.org/stable/c/a98172e36e5f1b3d29ad71fade2d611cfcc2fe6f
https://git.kernel.org/stable/c/cbc7c29dff0fa18162f2a3889d82eeefd67305e0
https://git.kernel.org/stable/c/2fa74d29fc1899c237d51bf9a6e132ea5c488976
https://git.kernel.org/stable/c/2c9de867ca285c397cd71af703763fe416265706
https://git.kernel.org/stable/c/9034c87d61be8cff989017740a91701ac8195a1d
https://git.kernel.org/stable/c/bb32500fb9b78215e4ef6ee8b4345c5f5d7eafb4

Timeline