kern/77234: corrupted data is read from UDF filesystem if read starts at non-aligned offset

[Andriy Gapon]

The following reply was made to PR kern/77234; it has been noted by GNATS.

From: Andriy Gapon <avg at icyb.net.ua>
To: FreeBSD-gnats-submit at FreeBSD.org, freebsd-bugs at FreeBSD.org
Cc:  
Subject: Re: kern/77234: corrupted data is read from UDF filesystem if read
 starts at non-aligned offset
Date: Mon, 7 Feb 2005 23:31:30 +0200 (EET)

 If meaning of max_size is interpreted as maximum number of contiguous 
 bytes that can be read starting from a given offset rather than starting 
 from a beginning of a calculated sector number then a patch could be like 
 the following. (Please note that currently max_size contains number of 
 bytes in an extent to which current offset belongs, which is total 
 nonsense since any code that calls udf_bmap_internal() has no notion of 
 extents)
 
 --- udf_vnops.c.orig	Mon Feb  7 22:59:34 2005
 +++ udf_vnops.c	Mon Feb  7 23:18:06 2005
 @@ -1107,19 +1107,21 @@
   		*size = max_size;
   	*size = min(*size, MAXBSIZE);
 
 -	if ((error = udf_readlblks(udfmp, sector, *size, bp))) {
 +	if ((error = udf_readlblks(udfmp, sector, *size + (offset & udfmp->bmask), bp))) {
   		printf("warning: udf_readlblks returned error %d\n", error);
   		return (error);
   	}
 
   	bp1 = *bp;
 -	*data = (uint8_t *)&bp1->b_data[offset % udfmp->bsize];
 +	*data = (uint8_t *)&bp1->b_data[offset & udfmp->bmask];
   	return (0);
   }
 
   /*
    * Translate a file offset into a logical block and then into a physical
    * block.
 + * max_size - maximum number of bytes that can be read starting from given
 + * offset, not beginning of calculated sector number
    */
   static int
   udf_bmap_internal(struct udf_node *node, off_t offset, daddr_t *sector, uint32_t *max_size)
 @@ -1172,7 +1174,7 @@
   		lsector = (offset  >> udfmp->bshift) +
   		    ((struct short_ad *)(icb))->pos;
 
 -		*max_size = GETICBLEN(short_ad, icb);
 +		*max_size = icblen - offset;
 
   		break;
   	case 1:
 @@ -1196,7 +1198,7 @@
   		lsector = (offset >> udfmp->bshift) +
   		    ((struct long_ad *)(icb))->loc.lb_num;
 
 -		*max_size = GETICBLEN(long_ad, icb);
 +		*max_size = icblen - offset;
 
   		break;
   	case 3: