issue: Check for resident hugepages to avoid SIGBUS

In a containerized environment mmap() beyond the hugepages limit can be
successful, but a further memory access triggers SIGBUS and terminates
the process. Check that all the allocated hugepages are resident with
mincore() to avoid the SIGBUS issue.

Signed-off-by: Dmytro Podgornyi <[email protected]>

src/core/util/hugepage_mgr.cpp

@@ -113,7 +113,34 @@ void *hugepage_mgr::alloc_hugepages_helper(size_t &size, size_t hugepage)
         ptr = nullptr;
         __log_info_dbg("mmap failed (errno=%d), skipping hugepage %zu kB", errno, hugepage / 1024U);
     } else {
-        size = actual_size;
+        // Check whether all the pages are resident. In a container, allocation beyond the limit can
+        // be successful and lead to SIGBUS on an access.
+        const size_t pages_nr = actual_size / hugepage;
+        size_t resident_nr = 0;
+        char *page_ptr = reinterpret_cast<char *>(ptr);
+        int rc = 0;
+
+        for (size_t i = 0; rc == 0 && i < pages_nr; ++i) {
+            unsigned char vec;
+            rc = mincore(page_ptr, 1, &vec);
+            resident_nr += rc == 0 ? (vec & 1U) : 0;
+            page_ptr += hugepage;
+        }
+
+        if (rc != 0 || resident_nr != pages_nr) {
+            munmap(ptr, actual_size);
+            ptr = nullptr;
+            if (rc < 0) {
+                __log_info_dbg("mincore() failed to verify hugepages (errno=%d)", errno);
+            } else if (resident_nr != pages_nr) {
+                __log_info_dbg("Not all hugepages are resident (allocated=%zu resident=%zu)",
+                               pages_nr, resident_nr);
+            }
+            __log_info_dbg("Cannot use hugepages, skipping hugepage %zu kB", hugepage / 1024U);
+        } else {
+            // Success.
+            size = actual_size;
+        }
     }
     return ptr;
 }