diskio: check early for an impossible LBA value for CHS requests

Make sure we don't end up trying to do a CHS request for a truly
absurd value, that could possibly be misconverted.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/core/fs/diskio.c b/core/fs/diskio.c
index 822314c..cf9bf49 100644 (file)
--- a/core/fs/diskio.c
+++ b/core/fs/diskio.c
@@ -25,6 +25,9 @@ static int chs_rdwr_sectors(struct disk *disk, void *buf,
     int retry;
     uint32_t maxtransfer = disk->maxtransfer;
 
+    if (lba + disk->part_start >= 1024*256*63)
+       return 0;               /* Impossible CHS request */
+
     memset(&ireg, 0, sizeof ireg);
 
     ireg.eax.b[1] = 0x02 + is_write;