This is a note to let you know that I've just added the patch titled
Bluetooth: Fix atomicity violation in {min,max}_key_size_set
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bluetooth-fix-atomicity-violation-in-min-max-_key_size_set.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From da9065caa594d19b26e1a030fd0cc27bd365d685 Mon Sep 17 00:00:00 2001
From: Gui-Dong Han <2045gemini@xxxxxxxxx>
Date: Fri, 22 Dec 2023 23:12:41 +0800
Subject: Bluetooth: Fix atomicity violation in {min,max}_key_size_set
From: Gui-Dong Han <2045gemini@xxxxxxxxx>
commit da9065caa594d19b26e1a030fd0cc27bd365d685 upstream.
In min_key_size_set():
if (val > hdev->le_max_key_size || val < SMP_MIN_ENC_KEY_SIZE)
return -EINVAL;
hci_dev_lock(hdev);
hdev->le_min_key_size = val;
hci_dev_unlock(hdev);
In max_key_size_set():
if (val > SMP_MAX_ENC_KEY_SIZE || val < hdev->le_min_key_size)
return -EINVAL;
hci_dev_lock(hdev);
hdev->le_max_key_size = val;
hci_dev_unlock(hdev);
The atomicity violation occurs due to concurrent execution of set_min and
set_max funcs.Consider a scenario where setmin writes a new, valid 'min'
value, and concurrently, setmax writes a value that is greater than the
old 'min' but smaller than the new 'min'. In this case, setmax might check
against the old 'min' value (before acquiring the lock) but write its
value after the 'min' has been updated by setmin. This leads to a
situation where the 'max' value ends up being smaller than the 'min'
value, which is an inconsistency.
This possible bug is found by an experimental static analysis tool
developed by our team, BassCheck[1]. This tool analyzes the locking APIs
to extract function pairs that can be concurrently executed, and then
analyzes the instructions in the paired functions to identify possible
concurrency bugs including data races and atomicity violations. The above
possible bug is reported when our tool analyzes the source code of
Linux 5.17.
To resolve this issue, it is suggested to encompass the validity checks
within the locked sections in both set_min and set_max funcs. The
modification ensures that the validation of 'val' against the
current min/max values is atomic, thus maintaining the integrity of the
settings. With this patch applied, our tool no longer reports the bug,
with the kernel configuration allyesconfig for x86_64. Due to the lack of
associated hardware, we cannot test the patch in runtime testing, and just
verify it according to the code logic.
[1] https://sites.google.com/view/basscheck/
Fixes: 18f81241b74f ("Bluetooth: Move {min,max}_key_size debugfs ...")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gui-Dong Han <2045gemini@xxxxxxxxx>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/bluetooth/hci_debugfs.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--- a/net/bluetooth/hci_debugfs.c
+++ b/net/bluetooth/hci_debugfs.c
@@ -1044,10 +1044,12 @@ static int min_key_size_set(void *data,
{
struct hci_dev *hdev = data;
- if (val > hdev->le_max_key_size || val < SMP_MIN_ENC_KEY_SIZE)
+ hci_dev_lock(hdev);
+ if (val > hdev->le_max_key_size || val < SMP_MIN_ENC_KEY_SIZE) {
+ hci_dev_unlock(hdev);
return -EINVAL;
+ }
- hci_dev_lock(hdev);
hdev->le_min_key_size = val;
hci_dev_unlock(hdev);
@@ -1072,10 +1074,12 @@ static int max_key_size_set(void *data,
{
struct hci_dev *hdev = data;
- if (val > SMP_MAX_ENC_KEY_SIZE || val < hdev->le_min_key_size)
+ hci_dev_lock(hdev);
+ if (val > SMP_MAX_ENC_KEY_SIZE || val < hdev->le_min_key_size) {
+ hci_dev_unlock(hdev);
return -EINVAL;
+ }
- hci_dev_lock(hdev);
hdev->le_max_key_size = val;
hci_dev_unlock(hdev);
Patches currently in stable-queue which might be from 2045gemini@xxxxxxxxx are
queue-5.15/usb-mon-fix-atomicity-violation-in-mon_bin_vma_fault.patch
queue-5.15/bluetooth-fix-atomicity-violation-in-min-max-_key_size_set.patch
