diff options
| author | Marco Elver <elver@google.com> | 2020-01-29 16:01:02 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-03-21 09:41:29 +0100 |
| commit | ad4f8eeca8eaa24afb6059c241a2f4baf86378f3 (patch) | |
| tree | 21f97518ec07d2b4cb94946b4b7be15a540023e9 /kernel/kcsan | |
| parent | f1bc96210c6a6b853b4b2eec808141956e8fbc5d (diff) | |
kcsan: Address missing case with KCSAN_REPORT_VALUE_CHANGE_ONLY
Even with KCSAN_REPORT_VALUE_CHANGE_ONLY, KCSAN still reports data
races between reads and watchpointed writes, even if the writes wrote
values already present. This commit causes KCSAN to unconditionally
skip reporting in this case.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/kcsan')
| -rw-r--r-- | kernel/kcsan/report.c | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 33bdf8b229b5..7cd34285df74 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -130,12 +130,25 @@ static bool rate_limit_report(unsigned long frame1, unsigned long frame2) * Special rules to skip reporting. */ static bool -skip_report(int access_type, bool value_change, unsigned long top_frame) +skip_report(bool value_change, unsigned long top_frame) { - const bool is_write = (access_type & KCSAN_ACCESS_WRITE) != 0; - - if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && is_write && - !value_change) { + /* + * The first call to skip_report always has value_change==true, since we + * cannot know the value written of an instrumented access. For the 2nd + * call there are 6 cases with CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY: + * + * 1. read watchpoint, conflicting write (value_change==true): report; + * 2. read watchpoint, conflicting write (value_change==false): skip; + * 3. write watchpoint, conflicting write (value_change==true): report; + * 4. write watchpoint, conflicting write (value_change==false): skip; + * 5. write watchpoint, conflicting read (value_change==false): skip; + * 6. write watchpoint, conflicting read (value_change==true): impossible; + * + * Cases 1-4 are intuitive and expected; case 5 ensures we do not report + * data races where the write may have rewritten the same value; and + * case 6 is simply impossible. + */ + if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && !value_change) { /* * The access is a write, but the data value did not change. * @@ -228,7 +241,7 @@ static bool print_report(const volatile void *ptr, size_t size, int access_type, /* * Must check report filter rules before starting to print. */ - if (skip_report(access_type, true, stack_entries[skipnr])) + if (skip_report(true, stack_entries[skipnr])) return false; if (type == KCSAN_REPORT_RACE_SIGNAL) { @@ -237,7 +250,7 @@ static bool print_report(const volatile void *ptr, size_t size, int access_type, other_frame = other_info.stack_entries[other_skipnr]; /* @value_change is only known for the other thread */ - if (skip_report(other_info.access_type, value_change, other_frame)) + if (skip_report(value_change, other_frame)) return false; } |