Re: Avoid incomplete copy string (src/backend/access/transam/xlog.c)

Em dom., 23 de jun. de 2024 às 23:56, Richard Guo <guofenglinux@gmail.com>
escreveu:

> On Mon, Jun 24, 2024 at 7:51 AM Ranier Vilela <ranier.vf@gmail.com> wrote:
> > In src/include/access/xlogbackup.h, the field *name*
> > has one byte extra to store null-termination.
> >
> > But, in the function *do_pg_backup_start*,
> > I think that is a mistake in the line (8736):
> >
> > memcpy(state->name, backupidstr, strlen(backupidstr));
> >
> > memcpy with strlen does not copy the whole string.
> > strlen returns the exact length of the string, without
> > the null-termination.
>
> I noticed that the two callers of do_pg_backup_start both allocate
> BackupState with palloc0.  Can we rely on this to ensure that the
> BackupState.name is initialized with null-termination?
>
I do not think so.
It seems to me the best solution is to use Michael's suggestion, strlcpy +
sizeof.

Currently we have this:
memcpy(state->name, "longlongpathexample1",
strlen("longlongpathexample1"));
printf("%s\n", state->name);
longlongpathexample1

Next random call:
memcpy(state->name, "longpathexample2", strlen("longpathexample2"));
printf("%s\n", state->name);
longpathexample2ple1

It's not a good idea to use memcpy with strlen.

best regards,
Ranier Vilela