lib-index: Assert-crashfix on some rare situations.

mail_index_modseq_get_next_log_offset() might have returned e.g. (seq=4,
offset=40) to point to the beginning of a next file. The view itself could
still have been pointing to seq=3 end of file. Now calling
mail_transaction_log_view_set() with these two positions (that are basically
the same) should result in an empty view instead of assert crash.

diff --git a/src/lib-index/mail-transaction-log-view.c b/src/lib-index/mail-transaction-log-view.c
index 60f594e4d864f5143e0b21646125a544bb5668a1..852fe08446884938b57de62ded38f3234c0a4ba6 100644 (file)
--- a/src/lib-index/mail-transaction-log-view.c
+++ b/src/lib-index/mail-transaction-log-view.c
@@ -63,14 +63,12 @@ int mail_transaction_log_view_set(struct mail_transaction_log_view *view,
                                  uint32_t max_file_seq, uoff_t max_file_offset,
                                  bool *reset_r)
 {
-       struct mail_transaction_log_file *file, *const *files, *tail;
+       struct mail_transaction_log_file *file, *const *files;
        uoff_t start_offset, end_offset;
        unsigned int i;
        uint32_t seq;
        int ret;
 
-       i_assert(min_file_seq <= max_file_seq);
-
        *reset_r = FALSE;
 
        if (view->log == NULL) {
@@ -79,28 +77,35 @@ int mail_transaction_log_view_set(struct mail_transaction_log_view *view,
                return -1;
        }
 
-       tail = view->log->files;
        if (min_file_seq == 0) {
                /* index file doesn't exist yet. this transaction log should
                   start from the beginning */
-               if (tail->hdr.prev_file_seq != 0) {
+               if (view->log->files->hdr.prev_file_seq != 0) {
                        /* but it doesn't */
                        return 0;
                }
 
-               min_file_seq = tail->hdr.file_seq;
+               min_file_seq = view->log->files->hdr.file_seq;
                min_file_offset = 0;
 
                if (max_file_seq == 0) {
                        max_file_seq = min_file_seq;
                        max_file_offset = min_file_offset;
                }
-       } 
+       }
 
-       if (min_file_seq == tail->hdr.prev_file_seq &&
-           min_file_offset == tail->hdr.prev_file_offset) {
-               /* we can skip this */
-               min_file_seq = tail->hdr.file_seq;
+       for (file = view->log->files; file != NULL; file = file->next) {
+               if (file->hdr.prev_file_seq == min_file_seq)
+                       break;
+       }
+       if (file != NULL && min_file_offset == file->hdr.prev_file_offset) {
+               /* we can skip to the next file. we've delayed checking for
+                  min_file_seq <= max_file_seq until now, because it's not
+                  really an error to specify the same position twice (even if
+                  in "wrong" order) */
+               i_assert(min_file_seq <= max_file_seq ||
+                        file->hdr.file_seq <= max_file_seq);
+               min_file_seq = file->hdr.file_seq;
                min_file_offset = 0;
 
                if (min_file_seq > max_file_seq) {
@@ -108,6 +113,8 @@ int mail_transaction_log_view_set(struct mail_transaction_log_view *view,
                        max_file_seq = min_file_seq;
                        max_file_offset = min_file_offset;
                }
+       } else {
+               i_assert(min_file_seq <= max_file_seq);
        }
 
        if (min_file_seq == max_file_seq && min_file_offset > max_file_offset) {
@@ -119,12 +126,13 @@ int mail_transaction_log_view_set(struct mail_transaction_log_view *view,
                return -1;
        }
 
-       if (min_file_offset > 0 && min_file_offset < tail->hdr.hdr_size) {
+       if (min_file_offset > 0 && file != NULL &&
+           min_file_offset < file->hdr.hdr_size) {
                /* log file offset is probably corrupted in the index file. */
                mail_transaction_log_view_set_corrupted(view,
                        "file_seq=%u, min_file_offset (%"PRIuUOFF_T
                        ") < hdr_size (%u)",
-                       min_file_seq, min_file_offset, tail->hdr.hdr_size);
+                       min_file_seq, min_file_offset, file->hdr.hdr_size);
                return -1;
        }