From: Mark Wielaard <mark@klomp.org>
Date: Tue, 12 Nov 2024 12:34:09 +0000 (+0100)
Subject: vgdb.c (fork_and_exec_valgrind): Fix another off-by-one error write
X-Git-Tag: VALGRIND_3_25_0~240
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=747ca4eb5fed5dd58a14391a997bb9e658e3b1c8;p=thirdparty%2Fvalgrind.git

vgdb.c (fork_and_exec_valgrind): Fix another off-by-one error write

commit 646978d9adc5 ("vgdb: Handle EINTR and EAGAIN more
consistently") introduced another off-by-one issue trying to write
back the error from child to parent.

Instead of +1 it should have been +written (which initially is zero).

This is when the child needs to do a chdir and that chdir fails. If
that happens the parent would have gotten the wrong error code.
---

diff --git a/coregrind/vgdb.c b/coregrind/vgdb.c
index 90e3f1502..409ceac5d 100644
--- a/coregrind/vgdb.c
+++ b/coregrind/vgdb.c
@@ -1289,7 +1289,7 @@ int fork_and_exec_valgrind (int argc, char **argv, const char *working_dir,
             // We try to write the result to the parent, but always exit.
             size_t written = 0;
             while (written < sizeof (int)) {
-               int nrw = write (pipefd[1], ((char *)&err) + 1,
+               int nrw = write (pipefd[1], ((char *)&err) + written,
                                 sizeof (int) - written);
                if (nrw == -1) {
                   if (errno == EINTR || errno == EAGAIN)