Re: Avoid incomplete copy string (src/backend/access/transam/xlog.c) - Mailing list pgsql-hackers

From Ranier Vilela
Subject Re: Avoid incomplete copy string (src/backend/access/transam/xlog.c)
Date
Msg-id CAEudQAqqRYns_JVGJeCg=wUxozitCDrh=GNvGJdcN=4yKpLD_Q@mail.gmail.com
Whole thread Raw
In response to Re: Avoid incomplete copy string (src/backend/access/transam/xlog.c)  (Fabrízio de Royes Mello <fabriziomello@gmail.com>)
List pgsql-hackers
Em dom., 23 de jun. de 2024 às 21:08, Fabrízio de Royes Mello <fabriziomello@gmail.com> escreveu:

On Sun, 23 Jun 2024 at 20:51 Ranier Vilela <ranier.vf@gmail.com> wrote:
Hi.

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.

So, I think this can result in errors,
like in the function *build_backup_content* (src/backend/access/transam/xlogbackup.c)
Where *appendStringInfo* expects a string with null-termination.

appendStringInfo(result, "LABEL: %s\n", state->name);

To fix, copy strlen size plus one byte, to include the null-termination.


Doesn’t “sizeof” solve the problem? It take in account the null-termination character.
sizeof is is preferable when dealing with constants such as:
memcpy(name, "string test1", sizeof( "string test1");

Using sizeof in this case will always copy MAXPGPATH + 1.
Modern compilers will optimize strlen,
copying fewer bytes.

best regards,
Ranier Vilela

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