[PULL,09/16] pc-bios/s390-ccw: fix off-by-one error

Commit Message

Thomas Huth Oct. 6, 2020, 6:31 p.m. UTC

From: Marc Hartmayer <[e-mail]>

This error takes effect when the magic value "zIPL" is located at the
end of a block. For example if s2_cur_blk = 0x7fe18000 and the magic
value "zIPL" is located at 0x7fe18ffc - 0x7fe18fff.

Fixes: ba831b25262a ("s390-ccw: read stage2 boot loader data to find menu")
Reviewed-by: Collin Walling <[e-mail]>
Signed-off-by: Marc Hartmayer <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Thomas Huth <[e-mail]>
[thuth: Use "<= ... - 4" instead of "< ... - 3"]
Signed-off-by: Thomas Huth <[e-mail]>
---
 pc-bios/s390-ccw/bootmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
index 0ef6b851f3..767bb612db 100644
--- a/pc-bios/s390-ccw/bootmap.c
+++ b/pc-bios/s390-ccw/bootmap.c
@@ -163,7 +163,7 @@  static bool find_zipl_boot_menu_banner(int *offset)
     int i;
 
     /* Menu banner starts with "zIPL" */
-    for (i = 0; i < virtio_get_block_size() - 4; i++) {
+    for (i = 0; i <= virtio_get_block_size() - 4; i++) {
         if (magic_match(s2_cur_blk + i, ZIPL_MAGIC_EBCDIC)) {
             *offset = i;
             return true;