On Mon, Dec 18, 2017 at 03:18:37PM +0800, Michael W. Bombardieri wrote:
> Hello,
>
> In my understanding the reason why texec had to be static was
> because the struct member ioact was never initialised.
> The call tree is execute() -> comexec() -> exchild() -> execute()
> and a fork happens in exchild().
> The second execute() dereferences t->ioact on line 115 which causes
> SEGV. Setting ioact to NULL explicitly seems better than
> doing this via "static".
> Does this work for you?
>
> - Michael
>
>
> Index: exec.c
> ===================================================================
> RCS file: /cvs/src/bin/ksh/exec.c,v
> retrieving revision 1.68
> diff -u -p -u -r1.68 exec.c
> --- exec.c 11 Dec 2016 17:49:19 -0000 1.68
> +++ exec.c 18 Dec 2017 07:05:47 -0000
> @@ -409,7 +409,7 @@ comexec(struct op *t, struct tbl *volati
> volatile int rv = 0;
> char *cp;
> char **lastp;
> - static struct op texec; /* Must be static (XXX but why?) */
> + struct op texec;
> int type_flags;
> int keepasn_ok;
> int fcflags = FC_BI|FC_FUNC|FC_PATH;
> @@ -688,6 +688,7 @@ comexec(struct op *t, struct tbl *volati
> texec.left = t; /* for tprint */
> texec.str = tp->val.s;
> texec.args = ap;
> + texec.ioact = NULL;
> rv = exchild(&texec, flags, xerrok, -1);
> break;
> }
>
Good analysis. I would go even further and zero out texec completely.
Comments? OK?
Index: exec.c
===================================================================
RCS file: /cvs/src/bin/ksh/exec.c,v
retrieving revision 1.68
diff -u -p -r1.68 exec.c
--- exec.c 11 Dec 2016 17:49:19 -0000 1.68
+++ exec.c 18 Dec 2017 19:35:16 -0000
@@ -409,7 +409,7 @@ comexec(struct op *t, struct tbl *volati
volatile int rv = 0;
char *cp;
char **lastp;
- static struct op texec; /* Must be static (XXX but why?) */
+ struct op texec;
int type_flags;
int keepasn_ok;
int fcflags = FC_BI|FC_FUNC|FC_PATH;
@@ -684,6 +684,7 @@ comexec(struct op *t, struct tbl *volati
}
/* to fork we set up a TEXEC node and call execute */
+ memset(&texec, 0, sizeof(texec));
texec.type = TEXEC;
texec.left = t; /* for tprint */
texec.str = tp->val.s;
