LTTng » LTTng-tools

Hi

If lttng-sessiond terminates unexpectedly after truncating the metadata file from --shm-path path (when doing metadata regenerate), afterwards when trying to recover the trace buffers using lttng-crash <- it Bus error (core dumped). This translates to:

$ lttng create s1 --shm-path=/tmp/test-lttng
$ lttng enable-event -u -a -s s1
$ lttng start
$ <path>/lttng-tools/tests/utils/testapp/gen-ust-events/gen-ust-events
$ pkill -9 "lttng-" # 1
$ cp /dev/null /tmp/test/s1-*/ust/uid/1000/64-bit/metadata # 2 - 1 and 2 simulate sessiond crash immediately after ftruncate() during metadata regenerate
$ lttng-crash --viewer=babeltrace /tmp/test-lttng/

A possible fix is :

---
 src/bin/lttng-crash/lttng-crash.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/bin/lttng-crash/lttng-crash.c b/src/bin/lttng-crash/lttng-crash.c
index ba28af9..0fb93fd 100644
--- a/src/bin/lttng-crash/lttng-crash.c
+++ b/src/bin/lttng-crash/lttng-crash.c
@@ -490,7 +490,8 @@ int check_magic(const uint8_t *magic)
 }

 static
-int get_crash_layout(struct lttng_crash_layout *layout, int fd)
+int get_crash_layout(struct lttng_crash_layout *layout, int fd,
+    const char *input_path, const char *input_file)
 {
     char *map;
     int ret = 0, unmapret;
@@ -501,7 +502,13 @@ int get_crash_layout(struct lttng_crash_layout *layout, int fd)
     const struct crash_abi_unknown *abi;
     uint16_t endian;
     enum lttng_crash_type layout_type;
+    struct stat sb;

+    fstat(fd, &sb);
+    if (sb.st_size <  RB_CRASH_DUMP_ABI_LEN) {
+        ERR("File truncated: %s/%s", input_path, input_file);
+        return -1;
+    }
     map = mmap(NULL, RB_CRASH_DUMP_ABI_LEN, PROT_READ, MAP_PRIVATE,
         fd, 0);
     if (map == MAP_FAILED) {
@@ -830,7 +837,7 @@ int extract_file(int output_dir_fd, const char *output_file,
     }

     /* Query the crash ABI layout */
-    ret = get_crash_layout(&layout, fd_src);
+    ret = get_crash_layout(&layout, fd_src, input_path, input_file);
     if (ret) {
         goto close_src;
     }
-- 
1.9.1