| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2023-52879: tracing: Have trace_event_file have ref counters |
| |
| 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 still opened by user space, it will not be |
| totally removed until the final dput() is called on it. But this is not |
| true with the event "file" descriptor that is already freed. If the user |
| does a write to or simply closes the file descriptor it will reference the |
| event "file" descriptor that was just freed, causing a use-after-free bug. |
| |
| To solve this, add a ref count to the event "file" descriptor as well as a |
| new flag called "FREED". The "file" will not be freed until the last |
| reference is released. But the FREE flag will be set when the event is |
| removed to prevent any more modifications to that event from happening, |
| even if there's still a reference to the event "file" descriptor. |
| |
| The Linux kernel CVE team has assigned CVE-2023-52879 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.4.258 with commit e6807c873d8791ae5a5186ad05ec66cab926539a and fixed in 5.4.262 with commit 961c4511c7578d6b8f39118be919016ec3db1c1e |
| Issue introduced in 5.10.198 with commit 407bf1c140f0757706c0b28604bcc90837d45ce2 and fixed in 5.10.202 with commit a98172e36e5f1b3d29ad71fade2d611cfcc2fe6f |
| Issue introduced in 5.15.134 with commit fa6d449e4d024d8c17f4288e0567d28ace69415c and fixed in 5.15.140 with commit cbc7c29dff0fa18162f2a3889d82eeefd67305e0 |
| Issue introduced in 6.1.55 with commit a46bf337a20f9edd3c8041b025639842280d0575 and fixed in 6.1.64 with commit 2fa74d29fc1899c237d51bf9a6e132ea5c488976 |
| Issue introduced in 6.5.5 with commit 9beec04370132a7a6cd1aa9897f6fffc6262ff28 and fixed in 6.5.13 with commit 2c9de867ca285c397cd71af703763fe416265706 |
| Issue introduced in 6.6 with commit f5ca233e2e66dc1c249bf07eefa37e34a6c9346a and fixed in 6.6.1 with commit 9034c87d61be8cff989017740a91701ac8195a1d |
| Issue introduced in 6.6 with commit f5ca233e2e66dc1c249bf07eefa37e34a6c9346a and fixed in 6.7 with commit bb32500fb9b78215e4ef6ee8b4345c5f5d7eafb4 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2023-52879 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| include/linux/trace_events.h |
| kernel/trace/trace.c |
| kernel/trace/trace.h |
| kernel/trace/trace_events.c |
| kernel/trace/trace_events_filter.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| 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 |
