Re: [PATCH] Fix regression when unsetting variables.

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxxx>]

On Wed, Jun 16, 2010 at 02:29:58AM +0000, Brian Koropoff wrote:
> When removing a variable from its hash chain, assign to the 'next' pointer
> of the previous link rather than the hash bucket.

OK I ended up fixing it slightly differently.

commit cb20b2cd727c892756ff3f144ebf92feb5590562
Author: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date:   Tue Jul 6 17:40:53 2010 +0800

    [VAR] Fix loss of variables when hash collides
    
    Brian Koropoff reported that the new var patches broke the following
    script:
    
    #!/bin/dash
    GDM_LANG="bar"
    OPTION="foo"
    unset GDM_LANG
    # OPTION has mysteriously become unset
    echo "$OPTION"
    
    He correctly diagnosed this as a result of removing all variables
    in the hash chain preceding the one that should be removed in
    setvareq.
    
    He also provided a patch to fix this.
    
    This patch is based on his but without keeping the original vpp.
    As a result, we now store new variables at the end of the hash
    chain instead of the beginning.
    
    To make this work, setvareq/setvar now returns the vp pointer
    modified.  In case they're used to unset a variable the pointer
    returned is undefined.  This is because mklocal needs it and
    used to get it by assuming that the new variable always appear
    at the beginning of the chain.
    
    Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

diff --git a/ChangeLog b/ChangeLog
index e45405c..48436b2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-07-06  Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
+
+	* Fix loss of variables when hash collides.
+
 2010-06-28  Gerrit Pape <pape@xxxxxxxxxxx>
 
 	* Don't clear eflag in evalbackcmd.
diff --git a/src/var.c b/src/var.c
index f456fbd..3efc943 100644
--- a/src/var.c
+++ b/src/var.c
@@ -180,13 +180,13 @@ initvar(void)
  * flags of the variable.  If val is NULL, the variable is unset.
  */
 
-void
-setvar(const char *name, const char *val, int flags)
+struct var *setvar(const char *name, const char *val, int flags)
 {
 	char *p, *q;
 	size_t namelen;
 	char *nameeq;
 	size_t vallen;
+	struct var *vp;
 
 	q = endofname(name);
 	p = strchrnul(q, '=');
@@ -206,8 +206,10 @@ setvar(const char *name, const char *val, int flags)
 		p = mempcpy(p, val, vallen);
 	}
 	*p = '\0';
-	setvareq(nameeq, flags | VNOSAVE);
+	vp = setvareq(nameeq, flags | VNOSAVE);
 	INTON;
+
+	return vp;
 }
 
 /*
@@ -235,14 +237,14 @@ intmax_t setvarint(const char *name, intmax_t val, int flags)
  * Called with interrupts off.
  */
 
-void
-setvareq(char *s, int flags)
+struct var *setvareq(char *s, int flags)
 {
 	struct var *vp, **vpp;
 
 	vpp = hashvar(s);
 	flags |= (VEXPORT & (((unsigned) (1 - aflag)) - 1));
-	vp = *findvar(vpp, s);
+	vpp = findvar(vpp, s);
+	vp = *vpp;
 	if (vp) {
 		if (vp->flags & VREADONLY) {
 			const char *n;
@@ -255,7 +257,7 @@ setvareq(char *s, int flags)
 		}
 
 		if (flags & VNOSET)
-			return;
+			goto out;
 
 		if (vp->func && (flags & VNOFUNC) == 0)
 			(*vp->func)(strchrnul(s, '=') + 1);
@@ -270,13 +272,13 @@ setvareq(char *s, int flags)
 out_free:
 			if ((flags & (VTEXTFIXED|VSTACK|VNOSAVE)) == VNOSAVE)
 				ckfree(s);
-			return;
+			goto out;
 		}
 
 		flags |= vp->flags & ~(VTEXTFIXED|VSTACK|VNOSAVE|VUNSET);
 	} else {
 		if (flags & VNOSET)
-			return;
+			goto out;
 		if ((flags & (VEXPORT|VREADONLY|VSTRFIXED|VUNSET)) == VUNSET)
 			goto out_free;
 		/* not found */
@@ -289,6 +291,9 @@ out_free:
 		s = savestr(s);
 	vp->text = s;
 	vp->flags = flags;
+
+out:
+	return vp;
 }
 
 
@@ -486,10 +491,9 @@ void mklocal(char *name)
 		eq = strchr(name, '=');
 		if (vp == NULL) {
 			if (eq)
-				setvareq(name, VSTRFIXED);
+				vp = setvareq(name, VSTRFIXED);
 			else
-				setvar(name, NULL, VSTRFIXED);
-			vp = *vpp;	/* the new variable */
+				vp = setvar(name, NULL, VSTRFIXED);
 			lvp->flags = VUNSET;
 		} else {
 			lvp->text = vp->text;
diff --git a/src/var.h b/src/var.h
index 7e7e505..7aa051f 100644
--- a/src/var.h
+++ b/src/var.h
@@ -128,9 +128,9 @@ extern const char defpathvar[];
 #define mpathset()	((vmpath.flags & VUNSET) == 0)
 
 void initvar(void);
-void setvar(const char *, const char *, int);
+struct var *setvar(const char *name, const char *val, int flags);
 intmax_t setvarint(const char *, intmax_t, int);
-void setvareq(char *, int);
+struct var *setvareq(char *s, int flags);
 struct strlist;
 void listsetvar(struct strlist *, int);
 char *lookupvar(const char *);

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe dash" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html