kernel: fix stat bugs

In a few places, we where using a fixed buffer of sizeof(Dir)+100
size for stat. This is not correct and fails if the name returned
in stat is long.

This results in being unable to seek to the end of file with a
long filename.

The kernel should do the same thing as dirfstat() from libc;
handling the conversion and buffer allocation and returning a
freeable Dir* pointer.

For this, a new dirchanstat() function was added.

The fstat syscall was not rewriting the name to the last path
element; fix it.

In addition, gracefully handle the mountfix case, reallocating
the buffer to accomidate the required stat length plus
size of the new name so dirsetname() does not fail.

1 files changed, 52 insertions, 60 deletions

diff --git a/sys/src/9/port/sysfile.c b/sys/src/9/port/sysfile.c
index 54cb64d02..1ead500a7 100644
--- a/sys/src/9/port/sysfile.c
+++ b/sys/src/9/port/sysfile.c
@@ -592,22 +592,26 @@ mountfix(Chan *c, uchar *op, long n, long maxn)
 			}
 			runlock(&mh->lock);
 
+			if(waserror())
+				goto Norewrite;
 			name = dirname(p, &nname);
-			/*
-			 * Do the stat but fix the name.  If it fails, leave old entry.
-			 * BUG: If it fails because there isn't room for the entry,
-			 * what can we do?  Nothing, really.  Might as well skip it.
-			 */
 			if(buf == nil){
 				nbuf = 4096;
 				buf = smalloc(nbuf);
 			}
-			if(waserror())
-				goto Norewrite;
 			l = devtab[nc->type]->stat(nc, buf, nbuf);
+			if(l < BIT16SZ)
+				error(Eshortstat);
+			rest = BIT16SZ + GBIT16(buf) + nname;
+			if(rest > nbuf){
+				free(buf);
+				nbuf = rest;
+				buf = smalloc(nbuf);
+				l = devtab[nc->type]->stat(nc, buf, nbuf);
+			}
 			l = dirsetname(name, nname, buf, l, nbuf);
-			if(l == BIT16SZ)
-				error("dirsetname");
+			if(l <= BIT16SZ)
+				error(Eshortstat);
 			poperror();
 
 			/*
@@ -831,10 +835,8 @@ syspwrite(va_list list)
 static vlong
 sseek(int fd, vlong o, int type)
 {
+	Dir *d;
 	Chan *c;
-	uchar buf[sizeof(Dir)+100];
-	Dir dir;
-	int n;
 	vlong off;
 
 	c = fdtochan(fd, -1, 1, 1);
@@ -872,10 +874,9 @@ sseek(int fd, vlong o, int type)
 	case 2:
 		if(c->qid.type & QTDIR)
 			error(Eisdir);
-		n = devtab[c->type]->stat(c, buf, sizeof buf);
-		if(convM2D(buf, n, &dir, nil) == 0)
-			error("internal error: stat error in seek");
-		off = dir.length + o;
+		d = dirchanstat(c);
+		off = d->length + o;
+		free(d);
 		if(off < 0)
 			error(Enegoff);
 		c->offset = off;
@@ -967,34 +968,36 @@ pathlast(Path *p)
 uintptr
 sysfstat(va_list list)
 {
+	char *name;
+	uchar *s;
 	Chan *c;
 	int fd;
-	uint l;
-	uchar *s;
+	uint l, r;
 
 	fd = va_arg(list, int);
 	s = va_arg(list, uchar*);
 	l = va_arg(list, uint);
 	validaddr((uintptr)s, l, 1);
-
 	c = fdtochan(fd, -1, 0, 1);
 	if(waserror()) {
 		cclose(c);
 		nexterror();
 	}
-	l = devtab[c->type]->stat(c, s, l);
+	r = devtab[c->type]->stat(c, s, l);
+	if((name = pathlast(c->path)) != nil)
+		r = dirsetname(name, strlen(name), s, r, l);
 	poperror();
 	cclose(c);
-	return l;
+	return r;
 }
 
 uintptr
 sysstat(va_list list)
 {
 	char *name;
+	uchar *s;
 	Chan *c;
 	uint l, r;
-	uchar *s;
 
 	name = va_arg(list, char*);
 	s = va_arg(list, uchar*);
@@ -1007,10 +1010,8 @@ sysstat(va_list list)
 		nexterror();
 	}
 	r = devtab[c->type]->stat(c, s, l);
-	name = pathlast(c->path);
-	if(name != nil)
+	if((name = pathlast(c->path)) != nil)
 		r = dirsetname(name, strlen(name), s, r, l);
-
 	poperror();
 	cclose(c);
 	return r;
@@ -1330,12 +1331,10 @@ packoldstat(uchar *buf, Dir *d)
 uintptr
 sys_stat(va_list list)
 {
-	static char old[] = "old stat system call - recompile";
+	char *name;
+	uchar *s;
 	Chan *c;
-	uint l;
-	uchar *s, buf[128];	/* old DIRLEN plus a little should be plenty */
-	char strs[128], *name;
-	Dir d;
+	Dir *d;
 
 	name = va_arg(list, char*);
 	s = va_arg(list, uchar*);
@@ -1346,18 +1345,16 @@ sys_stat(va_list list)
 		cclose(c);
 		nexterror();
 	}
-	l = devtab[c->type]->stat(c, buf, sizeof buf);
-	/* buf contains a new stat buf; convert to old. yuck. */
-	if(l <= BIT16SZ)	/* buffer too small; time to face reality */
-		error(old);
-	name = pathlast(c->path);
-	if(name != nil)
-		l = dirsetname(name, strlen(name), buf, l, sizeof buf);
-	l = convM2D(buf, l, &d, strs);
-	if(l == 0)
-		error(old);
-	packoldstat(s, &d);
-	
+	d = dirchanstat(c);
+	if(waserror()){
+		free(d);
+		nexterror();
+	}
+	if((name = pathlast(c->path)) != nil)
+		d->name = name;
+	packoldstat(s, d);
+	poperror();
+	free(d);
 	poperror();
 	cclose(c);
 	return 0;
@@ -1366,13 +1363,10 @@ sys_stat(va_list list)
 uintptr
 sys_fstat(va_list list)
 {
-	static char old[] = "old fstat system call - recompile";
-	Chan *c;
 	char *name;
-	uint l;
-	uchar *s, buf[128];	/* old DIRLEN plus a little should be plenty */
-	char strs[128];
-	Dir d;
+	uchar *s;
+	Chan *c;
+	Dir *d;
 	int fd;
 
 	fd = va_arg(list, int);
@@ -1383,18 +1377,16 @@ sys_fstat(va_list list)
 		cclose(c);
 		nexterror();
 	}
-	l = devtab[c->type]->stat(c, buf, sizeof buf);
-	/* buf contains a new stat buf; convert to old. yuck. */
-	if(l <= BIT16SZ)	/* buffer too small; time to face reality */
-		error(old);
-	name = pathlast(c->path);
-	if(name != nil)
-		l = dirsetname(name, strlen(name), buf, l, sizeof buf);
-	l = convM2D(buf, l, &d, strs);
-	if(l == 0)
-		error(old);
-	packoldstat(s, &d);
-	
+	d = dirchanstat(c);
+	if(waserror()){
+		free(d);
+		nexterror();
+	}
+	if((name = pathlast(c->path)) != nil)
+		d->name = name;
+	packoldstat(s, d);
+	poperror();
+	free(d);
 	poperror();
 	cclose(c);
 	return 0;