Thread: pg_dump fails to dump database

Mirek Hankus (M.Hankus@ce3.pl) reports a bug with a severity of 2
The lower the number the more severe it is.

Short Description
pg_dump fails to dump database

Long Description
pg_dump in postgreSQL 7.0.3 fails to dump database. Problem is becomeUser procedure in which lastusername stores
pointerto name of username which is currently connected. becomeUser is called for the first time in dumpSchema, which
allocatedmemory, calls becomeUser and then frees memory. Then becomeUser is called again during dumping of table data,
butlastusername points to deallocated memory, so it receives SIGSEGV (in strcmp).  

Solution.

   Use strdup to copy username, and do not use pointer to memory allocated in other procedures

In my case this bug made it imposible to backup database, upgrade also will be imposible.

Sample Code


No file was uploaded with this report

pgsql-bugs@postgresql.org writes:
> pg_dump in postgreSQL 7.0.3 fails to dump database. Problem is
> becomeUser procedure in which lastusername stores pointer to name of
> username which is currently connected. becomeUser is called for the
> first time in dumpSchema, which allocated memory, calls becomeUser and
> then frees memory. Then becomeUser is called again during dumping of
> table data, but lastusername points to deallocated memory, so it
> receives SIGSEGV (in strcmp).

Hm.  This is clearly erroneous code, but the odds of a coredump seem
*extremely* remote --- as borne out by the fact that this bug has been
in there for a good long while, and hasn't been noticed before.
strcmp as such isn't going to care whether the string it's pointed
at has been freed and/or overwritten.  It could only coredump if it
scanned past the end of physically allocated memory before hitting a
null, and that seems pretty unlikely, especially given that the other
input string is likely to be short.  What sort of platform are you
running on?

Philip, I see that becomeUser is toast in current sources, but it
seems like _reconnectAsUser might still have the same logic flaw;
wouldn't it be a good idea to make it strdup the value it saves in
currUser?

            regards, tom lane