Bug 27633 - low mem memory leaks
Summary: low mem memory leaks
Status: RESOLVED FIXED
Alias: None
Product: dwz
Classification: Unclassified
Component: default (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-03-23 11:05 UTC by Tom de Vries
Modified: 2021-03-24 17:08 UTC (History)
1 user (show)

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Description Tom de Vries 2021-03-23 11:05:41 UTC 
When building dwz with address sanitizer, we run into:
...
$ ./dwz hello -o hello.z -l0

=================================================================
==22607==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 432 byte(s) in 6 object(s) allocated from:
    #0 0x7f560af846d8 in __interceptor_calloc (/usr/lib64/libasan.so.4+0xdc6d8)
    #1 0x475db1 in htab_try_create /home/vries/dwz/dwz.git/hashtab.c:164
    #2 0x406ed6 in read_abbrev /home/vries/dwz/dwz.git/dwz.c:1296
    #3 0x42bca9 in read_debug_info /home/vries/dwz/dwz.git/dwz.c:6818
    #4 0x4608cb in read_dwarf /home/vries/dwz/dwz.git/dwz.c:13706
    #5 0x46ef9a in dwz /home/vries/dwz/dwz.git/dwz.c:15383
    #6 0x474a27 in dwz_one_file /home/vries/dwz/dwz.git/dwz.c:16279
    #7 0x475951 in main /home/vries/dwz/dwz.git/dwz.c:16450
    #8 0x7f560a8f9349 in __libc_start_main (/lib64/libc.so.6+0x24349)

Direct leak of 72 byte(s) in 1 object(s) allocated from:
    #0 0x7f560af846d8 in __interceptor_calloc (/usr/lib64/libasan.so.4+0xdc6d8)
    #1 0x475db1 in htab_try_create /home/vries/dwz/dwz.git/hashtab.c:164
    #2 0x42a8fd in read_debug_info /home/vries/dwz/dwz.git/dwz.c:6634
    #3 0x4608cb in read_dwarf /home/vries/dwz/dwz.git/dwz.c:13706
    #4 0x46ef9a in dwz /home/vries/dwz/dwz.git/dwz.c:15383
    #5 0x474a27 in dwz_one_file /home/vries/dwz/dwz.git/dwz.c:16279
    #6 0x475951 in main /home/vries/dwz/dwz.git/dwz.c:16450
    #7 0x7f560a8f9349 in __libc_start_main (/lib64/libc.so.6+0x24349)

Indirect leak of 4072 byte(s) in 1 object(s) allocated from:
    #0 0x7f560af846d8 in __interceptor_calloc (/usr/lib64/libasan.so.4+0xdc6d8)
    #1 0x475dd7 in htab_try_create /home/vries/dwz/dwz.git/hashtab.c:168
    #2 0x42a8fd in read_debug_info /home/vries/dwz/dwz.git/dwz.c:6634
    #3 0x4608cb in read_dwarf /home/vries/dwz/dwz.git/dwz.c:13706
    #4 0x46ef9a in dwz /home/vries/dwz/dwz.git/dwz.c:15383
    #5 0x474a27 in dwz_one_file /home/vries/dwz/dwz.git/dwz.c:16279
    #6 0x475951 in main /home/vries/dwz/dwz.git/dwz.c:16450
    #7 0x7f560a8f9349 in __libc_start_main (/lib64/libc.so.6+0x24349)

Indirect leak of 2928 byte(s) in 6 object(s) allocated from:
    #0 0x7f560af846d8 in __interceptor_calloc (/usr/lib64/libasan.so.4+0xdc6d8)
    #1 0x475dd7 in htab_try_create /home/vries/dwz/dwz.git/hashtab.c:168
    #2 0x406ed6 in read_abbrev /home/vries/dwz/dwz.git/dwz.c:1296
    #3 0x42bca9 in read_debug_info /home/vries/dwz/dwz.git/dwz.c:6818
    #4 0x4608cb in read_dwarf /home/vries/dwz/dwz.git/dwz.c:13706
    #5 0x46ef9a in dwz /home/vries/dwz/dwz.git/dwz.c:15383
    #6 0x474a27 in dwz_one_file /home/vries/dwz/dwz.git/dwz.c:16279
    #7 0x475951 in main /home/vries/dwz/dwz.git/dwz.c:16450
    #8 0x7f560a8f9349 in __libc_start_main (/lib64/libc.so.6+0x24349)

SUMMARY: AddressSanitizer: 7504 byte(s) leaked in 14 allocation(s).
...
Comment 1 Tom de Vries 2021-03-23 11:15:20 UTC 
Focusing on line 6634, we have:
...
  6631    if (unlikely (op_multifile || rd_multifile || fi_multifile || low_mem))
  6632      {
  6633        meta_abbrev_htab
  6634          = htab_try_create (500, meta_abbrev_hash, meta_abbrev_eq,
  6635                             meta_abbrev_del);
  6636        if (meta_abbrev_htab == NULL)
  6637          dwz_oom ();
  6638        to_free = obstack_alloc (&ob2, 1);
  6639      }
...

Doing a debug session while watching meta_abbrev_htab show us the problem.

First, we alloc:
...
Old value = (htab_t) 0x0
New value = (htab_t) 0x64f5e0
read_debug_info (dso=0x64c180, kind=0, die_count=0x0) at dwz.c:6636
6636          if (meta_abbrev_htab == NULL)
...

Then, we alloc again:
...
Old value = (htab_t) 0x64f5e0
New value = (htab_t) 0x651410
read_debug_info (dso=0x64c180, kind=5, die_count=0x0) at /home/vries/dwz/dwz.git/dwz.c:6636
6636          if (meta_abbrev_htab == NULL)
...
but this time, for .debug_types:
...
(gdb) up
#1  0x0000000000430660 in dwz (file=0x7fffffffe1d4 "hello", 
    outfile=0x7fffffffe1dd "hello.z", res=0x7fffffffdb80, resa=0x0, files=0x0)
    at /home/vries/dwz/dwz.git/dwz.c:15391
15391                  || read_debug_info (dso, DEBUG_TYPES, NULL)
...
Comment 2 Tom de Vries 2021-03-23 11:15:48 UTC 
This fixes it:
...
diff --git a/dwz.c b/dwz.c
index 4fc01a3..3dd4d5e 100644
--- a/dwz.c
+++ b/dwz.c
@@ -6628,7 +6628,8 @@ read_debug_info (DSO *dso, int kind, unsigned int *die_count)
       if (dup_htab == NULL)
        dwz_oom ();
     }
-  if (unlikely (op_multifile || rd_multifile || fi_multifile || low_mem))
+  if (meta_abbrev_htab == NULL
+      && unlikely (op_multifile || rd_multifile || fi_multifile || low_mem))
     {
       meta_abbrev_htab
        = htab_try_create (500, meta_abbrev_hash, meta_abbrev_eq,
...