From 546f8cfeca6fca0b6b246c8dbf035027e3f15f8c Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sat, 11 Sep 2021 12:26:35 +0000
Subject: [PATCH] 9boot: fix isowalk() for directories spanning multiple
 sectors

directory entries cannot span sector boundaries, meaning
that the end of a sector would be zero padded until the
next sector.

we have to skip over these zero paddings to fully read
the directory.
---
 sys/src/boot/efi/iso.c | 12 ++++++++----
 sys/src/boot/pc/iso.c  | 12 ++++++++----
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/sys/src/boot/efi/iso.c b/sys/src/boot/efi/iso.c
index 74e414a19..6a878667b 100644
--- a/sys/src/boot/efi/iso.c
+++ b/sys/src/boot/efi/iso.c
@@ -129,15 +129,19 @@ Foundpvd:
 		return 0;
 
 	for(;;){
-		if(readn(ex, &d, Dirsz) != Dirsz)
+		if(read(ex, &d.dirlen, 1) != 1)
 			break;
 		if(d.dirlen == 0)
+			continue;	/* zero padding to next sector */
+		if(read(ex, &d.dirlen + 1, Dirsz-1) != Dirsz-1)
 			break;
-		if(readn(ex, name, d.namelen) != d.namelen)
+		if(read(ex, name, d.namelen) != d.namelen)
 			break;
 		i = d.dirlen - (Dirsz + d.namelen);
-		while(i-- > 0)
-			read(ex, &c, 1);
+		while(i-- > 0){
+			if(read(ex, &c, 1) != 1)
+				break;
+		}
 		for(i=0; i<d.namelen; i++){
 			c = name[i];
 			if(c >= 'A' && c <= 'Z'){
diff --git a/sys/src/boot/pc/iso.c b/sys/src/boot/pc/iso.c
index e6a483902..d43ad4231 100644
--- a/sys/src/boot/pc/iso.c
+++ b/sys/src/boot/pc/iso.c
@@ -111,15 +111,19 @@ isowalk(Extend *ex, int drive, char *path)
 	ex->len = *((ulong*)(ex->buf + 156 + 10));
 
 	for(;;){
-		if(readn(ex, &d, Dirsz) != Dirsz)
+		if(read(ex, &d.dirlen, 1) != 1)
 			break;
 		if(d.dirlen == 0)
+			continue;	/* zero padding to next sector */
+		if(read(ex, &d.dirlen + 1, Dirsz-1) != Dirsz-1)
 			break;
-		if(readn(ex, name, d.namelen) != d.namelen)
+		if(read(ex, name, d.namelen) != d.namelen)
 			break;
 		i = d.dirlen - (Dirsz + d.namelen);
-		while(i-- > 0)
-			read(ex, &c, 1);
+		while(i-- > 0){
+			if(read(ex, &c, 1) != 1)
+				break;
+		}
 		for(i=0; i<d.namelen; i++){
 			c = name[i];
 			if(c >= 'A' && c <= 'Z'){