From fcf77515650272b9b51e18c115c66f48d33481b0 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Thu, 26 Jan 2017 09:31:40 +0000 Subject: [PATCH] [int13] Avoid potential division by zero Avoid using a zero sector count to guess the disk geometry, since that would result in a division by zero when calculating the number of cylinders. Signed-off-by: Michael Brown --- src/arch/x86/interface/pcbios/int13.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/src/arch/x86/interface/pcbios/int13.c b/src/arch/x86/interface/pcbios/int13.c index 6f16904d..8b2e134b 100644 --- a/src/arch/x86/interface/pcbios/int13.c +++ b/src/arch/x86/interface/pcbios/int13.c @@ -561,6 +561,8 @@ static int int13_guess_geometry_hdd ( struct int13_drive *int13, void *scratch, struct master_boot_record *mbr = scratch; struct partition_table_entry *partition; unsigned int i; + unsigned int end_head; + unsigned int end_sector; int rc; /* Default guess is xx/255/63 */ @@ -586,10 +588,12 @@ static int int13_guess_geometry_hdd ( struct int13_drive *int13, void *scratch, */ for ( i = 0 ; i < 4 ; i++ ) { partition = &mbr->partitions[i]; - if ( ! partition->type ) + end_head = PART_HEAD ( partition->chs_end ); + end_sector = PART_SECTOR ( partition->chs_end ); + if ( ! ( partition->type && end_head && end_sector ) ) continue; - *heads = ( PART_HEAD ( partition->chs_end ) + 1 ); - *sectors = PART_SECTOR ( partition->chs_end ); + *heads = ( end_head + 1 ); + *sectors = end_sector; DBGC ( int13, "INT13 drive %02x guessing C/H/S xx/%d/%d based " "on partition %d\n", int13->drive, *heads, *sectors, ( i + 1 ) );