While migrating an application from Microfocus to GnuCOBOL 2.0, I came across a bug when closing indexed files stored using Berkley DB, and COB_SYNC being true. When performing the CLOSE, the program core dumps with a SIGSEGV. I'm working from the gnu-cobol-2.0 SVN branch (r609), on Red Hat Linux 64bit.
Building the library with debugging gives details in the core dump stacktrace:
#0 0x00007f9ba4f70713 in cob_sync (f=0x112cde0) at fileio.c:657
#1 0x00007f9ba4f708b1 in save_status (f=0x112cde0, fnstatus=0x0, status=0)
at fileio.c:714
#2 0x00007f9ba4f777b4 in cob_close (f=0x112cde0, fnstatus=0x0, opt=0,
remfil=0) at fileio.c:4580
#3 0x00007f9ba4f7b93d in cob_exit_fileio () at fileio.c:6314
#4 0x00007f9ba4f5d5fe in cob_terminate_routines () at common.c:319
#5 0x00007f9ba4f5d859 in cob_sig_handler (sig=11) at common.c:432
#6 <signal handler called>
#7 0x00007f9ba4f70713 in cob_sync (f=0x112cc00) at fileio.c:657
#8 0x00007f9ba4f708b1 in save_status (f=0x112cc00, fnstatus=0x7f9b9ea218c0,
status=0) at fileio.c:714
#9 0x00007f9ba4f777b4 in cob_close (f=0x112cc00, fnstatus=0x7f9b9ea218c0,
opt=0, remfil=0) at fileio.c:4580
The problem is obvious enough: indexed_close is called, which closes the DB and frees the indexed_file structure in f->file, but that is then followed by save_status, where it tries to sync because COB_SYNC=Y and dereferences the f->file structure, causing the core dump.
That can be fixed by a simple "is open" test in either save_status or cob_sync. It also seems good style to NULL out the f->file pointer after closing the DB, rather than leaving a pointer to freed memory dangling.
I applied the following patch, which corrects the problem for us:
--- libcob/fileio.c (revision 609)
+++ libcob/fileio.c (working copy)
@@ -651,11 +651,13 @@
if (f->organization == COB_ORG_INDEXED) { #ifdef WITH_DB
p = f->file;
- for (i = 0; i < f->nkeys; ++i) {
- if (p->db[i]) {
- DB_SYNC (p->db[i]);
+ if (p) {
+ for (i = 0; i < f->nkeys; ++i) {
+ if (p->db[i]) {
+ DB_SYNC (p->db[i]);
+ }
+ }
}
#elif defined(WITH_ANY_ISAM)
fh = f->file;
if (fh) {
@@ -3283,6 +3285,9 @@
COB_UNUSED (opt);
p = f->file;
+ if (p == NULL) {
+ return COB_STATUS_00_SUCCESS;
+ }
/* Close DB's */
for (i = 0; i < (int)f->nkeys; ++i) {
if (p->cursor[i]) {
@@ -3313,6 +3318,7 @@
bdb_env->lock_id_free (bdb_env, p->bdb_lock_id);
}
cob_free (p);
+ f->file = NULL;
return COB_STATUS_00_SUCCESS;
And I'd just like to express our thanks for the wonderful effort that is GnuCOBOL. Keep up the good work!
Linton
-----
Linton Miller
Registration and Titling Solutions
Dealertrack Technologies
p 860-448-3177
www.dealertrack.com
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