LU-12420 utils: llog_reader handles uninitialized llog properly

When reading an empty LLOG, llog_reader would crash because
of record number of zero. E.g. "llog_reader CONFIGS/nodemap" on
a MGS without nodemap configuration would cause failure of:

llog_reader: Error allocating -16 bytes for recs_buf: Cannot allocate memory (12)
llog_reader: Could not pack buffer.: Cannot allocate memory (12)

After apply this patch, llog_reader will print following message
and quit if the LLOG is unintialized:

uninitialized llog: zero record number

Change-Id: I87246672e9fc992c99126134236c2e8d304df74b
Signed-off-by: Li Xi <lixi@ddn.com>
Reviewed-on: https://review.whamcloud.com/35177
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/utils/llog_reader.c b/lustre/utils/llog_reader.c
index 653ab18..e99dc35 100644 (file)
--- a/lustre/utils/llog_reader.c
+++ b/lustre/utils/llog_reader.c
@@ -196,8 +196,10 @@ int main(int argc, char **argv)
                goto out_fd;
        }
 
-       print_llog_header(llog_buf);
-       print_records(recs_buf, rec_number, is_ext);
+       if (llog_buf != NULL)
+               print_llog_header(llog_buf);
+       if (recs_buf != NULL)
+               print_records(recs_buf, rec_number, is_ext);
        llog_unpack_buffer(fd, llog_buf, recs_buf);
 
 out_fd:
@@ -218,6 +220,7 @@ int llog_pack_buffer(int fd, struct llog_log_hdr **llog,
        char *file_buf = NULL, *recs_buf = NULL;
        struct llog_rec_hdr **recs_pr = NULL;
        char *ptr = NULL;
+       int count;
        int i;
 
        rc = fstat(fd, &st);
@@ -259,8 +262,21 @@ int llog_pack_buffer(int fd, struct llog_log_hdr **llog,
                goto clear_file_buf;
        }
 
+       count = __le32_to_cpu((*llog)->llh_count);
+       if (count < 0) {
+               rc = -EINVAL;
+               llapi_error(LLAPI_MSG_ERROR, rc,
+                           "corrupted llog: negative record number %d",
+                           count);
+               goto clear_file_buf;
+       } else if (count == 0) {
+               llapi_printf(LLAPI_MSG_NORMAL,
+                            "uninitialized llog: zero record number\n");
+               *recs_number = 0;
+               goto clear_file_buf;
+       }
        /* the llog header not countable here.*/
-       recs_num = __le32_to_cpu((*llog)->llh_count) - 1;
+       recs_num = count - 1;
 
        recs_buf = malloc(recs_num * sizeof(**recs_pr));
        if (recs_buf == NULL) {
@@ -334,11 +350,13 @@ clear_file_buf:
 }
 
 void llog_unpack_buffer(int fd, struct llog_log_hdr *llog_buf,
-                        struct llog_rec_hdr **recs_buf)
+                       struct llog_rec_hdr **recs_buf)
 {
-        free(llog_buf);
-        free(recs_buf);
-        return;
+       if (llog_buf != NULL)
+               free(llog_buf);
+       if (recs_buf != NULL)
+               free(recs_buf);
+       return;
 }
 
 void print_llog_header(struct llog_log_hdr *llog_buf)