Bluetooth: Fix atomicity violation in conn_info_{min,max}_age_set
Subsystems (3)
PATCH 1/1 Bluetooth: Fix atomicity violation in conn_info_{min,max}_age_set
In conn_info_min_age_set():
if (val == 0 || val > hdev->conn_info_max_age) return -EINVAL; hci_dev_lock(hdev); hdev->conn_info_min_age = val; hci_dev_unlock(hdev);
In conn_info_max_age_set():
if (val == 0 || val < hdev->conn_info_min_age) return -EINVAL; hci_dev_lock(hdev); hdev->conn_info_max_age = val; hci_dev_unlock(hdev);
The atomicity violation occurs due to concurrent execution of set_min and set_max funcs which may lead to inconsistent reads and writes of the min value and the max value. The checks for value validity are ineffective as the min/max values could change immediately after being checked, raising the risk of the min value being greater than the max value and causing invalid settings.
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/
--- net/bluetooth/hci_debugfs.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
net/bluetooth/hci_debugfs.c +10 -6
@@ -217,11 +217,13 @@ DEFINE_SHOW_ATTRIBUTE(remote_oob);static int conn_info_min_age_set (void *data,u64 val) {struct hci_dev *hdev = data; - -if (val ==0 || val > hdev->conn_info_max_age) + +hci_dev_lock (hdev); +if (val ==0 || val > hdev->conn_info_max_age) { +hci_dev_unlock (hdev);return -EINVAL ; + } -hci_dev_lock (hdev); hdev->conn_info_min_age = val;hci_dev_unlock (hdev);
@@ -245,11 +247,13 @@ DEFINE_DEBUGFS_ATTRIBUTE(conn_info_min_age_fops, conn_info_min_age_get,static int conn_info_max_age_set (void *data,u64 val) {struct hci_dev *hdev = data; - -if (val ==0 || val < hdev->conn_info_min_age) + +hci_dev_lock (hdev); +if (val ==0 || val < hdev->conn_info_min_age) { +hci_dev_unlock (hdev);return -EINVAL ; + } -hci_dev_lock (hdev); hdev->conn_info_max_age = val;hci_dev_unlock (hdev);
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Dear submitter,
Thank you for submitting the patches to the linux bluetooth mailing list. This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=812456
---Test result---
Test Summary:
CheckPatch FAIL 2.32 seconds GitLint FAIL 1.55 seconds SubjectPrefix PASS 0.76 seconds BuildKernel PASS 27.54 seconds CheckAllWarning PASS 30.21 seconds CheckSparse PASS 35.96 seconds CheckSmatch PASS 102.31 seconds BuildKernel32 PASS 26.85 seconds TestRunnerSetup PASS 439.29 seconds TestRunner_l2cap-tester PASS 23.27 seconds TestRunner_iso-tester PASS 44.49 seconds TestRunner_bnep-tester PASS 7.46 seconds TestRunner_mgmt-tester PASS 175.71 seconds TestRunner_rfcomm-tester PASS 13.18 seconds TestRunner_sco-tester PASS 15.27 seconds TestRunner_ioctl-tester PASS 12.95 seconds TestRunner_mesh-tester PASS 9.61 seconds TestRunner_smp-tester PASS 10.60 seconds TestRunner_userchan-tester PASS 7.78 seconds IncrementalBuild PASS 29.06 seconds
Details
##############################
Test: CheckPatch - FAIL
Desc: Run checkpatch.pl script
Output:
Bluetooth: Fix atomicity violation in conn_info_{min,max}_age_set
WARNING: Please use correct Fixes: style 'Fixes: <12 chars of sha1> ("<title line>")' - ie: 'Fixes: ("Bluetooth: Move common debugfs file creation ...")' #121:
WARNING: Reported-by: should be immediately followed by Closes: with a URL to the report #123:
ERROR: trailing whitespace
#139: FILE: net/bluetooth/hci_debugfs.c:220:
+^I$
ERROR: trailing whitespace
#156: FILE: net/bluetooth/hci_debugfs.c:250:
+^I$
total: 2 errors, 2 warnings, 0 checks, 32 lines checked
NOTE: For some of the reported defects, checkpatch may be able to
mechanically convert to the typical style using --fix or --fix-inplace.
NOTE: Whitespace errors detected.
You may wish to use scripts/cleanpatch or scripts/cleanfile
/github/workspace/src/src/13503203.patch has style problems, please review.
NOTE: Ignored message types: UNKNOWN_COMMIT_ID
NOTE: If any of the errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.
Use of uninitialized value $cid in concatenation (.) or string at /github/workspace/src/src/scripts/checkpatch.pl line 3228.
##############################
Test: GitLint - FAIL
Desc: Run gitlint
Output:
Bluetooth: Fix atomicity violation in conn_info_{min,max}_age_set
WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
4: B3 Line contains hard tab characters (\t): " if (val == 0 || val > hdev->conn_info_max_age)"
5: B3 Line contains hard tab characters (\t): " return -EINVAL;"
6: B3 Line contains hard tab characters (\t): " hci_dev_lock(hdev);"
7: B3 Line contains hard tab characters (\t): " hdev->conn_info_min_age = val;"
8: B3 Line contains hard tab characters (\t): " hci_dev_unlock(hdev);"
11: B3 Line contains hard tab characters (\t): " if (val == 0 || val < hdev->conn_info_min_age)"
12: B3 Line contains hard tab characters (\t): " return -EINVAL;"
13: B3 Line contains hard tab characters (\t): " hci_dev_lock(hdev);"
14: B3 Line contains hard tab characters (\t): " hdev->conn_info_max_age = val;"
15: B3 Line contains hard tab characters (\t): " hci_dev_unlock(hdev);"
---
Regards,
Linux Bluetooth