diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/kcsan/report.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 3bc590e6be7e..abf6852dff72 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -422,6 +422,44 @@ retry: return false; } + access_type |= other_info.access_type; + if ((access_type & KCSAN_ACCESS_WRITE) == 0) { + /* + * While the address matches, this is not the other_info + * from the thread that consumed our watchpoint, since + * neither this nor the access in other_info is a write. + * It is invalid to continue with the report, since we + * only have information about reads. + * + * This can happen due to concurrent races on the same + * address, with at least 4 threads. To avoid locking up + * other_info and all other threads, we have to consume + * it regardless. + * + * A concrete case to illustrate why we might lock up if + * we do not consume other_info: + * + * We have 4 threads, all accessing the same address + * (or matching address ranges). Assume the following + * watcher and watchpoint consumer pairs: + * write1-read1, read2-write2. The first to populate + * other_info is write2, however, write1 consumes it, + * resulting in a report of write1-write2. This report + * is valid, however, now read1 populates other_info; + * read2-read1 is an invalid conflict, yet, no other + * conflicting access is left. Therefore, we must + * consume read1's other_info. + * + * Since this case is assumed to be rare, it is + * reasonable to omit this report: one of the other + * reports includes information about the same shared + * data, and at this point the likelihood that we + * re-report the same race again is high. + */ + release_report(flags, KCSAN_REPORT_RACE_SIGNAL); + return false; + } + /* * Matching & usable access in other_info: keep other_info_lock * locked, as this thread consumes it to print the full report; |