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Integer underflow in efipart_realstrategy when I/O starts after end of disk

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This fixes an integer underflow in efipart_realstrategy, which causes
crashes when an I/O operation's start point is after the end of the disk.
This can happen when trying to detect filesystems on very small disks.
This can occur if a BIOS freebsd-boot partition exists on a system when the
EFI loader is being used.

PR:		219000
Submitted by:	Eric McCorkle <eric@metricspace.net>
Reviewed by:	cem (previous version), tsoome (previous version)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D10559
This commit is contained in:
Allan Jude 2017-07-01 20:25:22 +00:00
parent 993d3ded79
commit e11bad9d2b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=320553
1 changed files with 10 additions and 1 deletions
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11
sys/boot/efi/libefi/efipart.c
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@ -888,6 +888,7 @@ efipart_realstrategy(void *devdata, int rw, daddr_t blk, size_t size,
char *blkbuf;
size_t blkoff, blksz;
int error;
size_t diskend, readstart;
if (dev == NULL || blk < 0)
return (EINVAL);
@ -925,7 +926,15 @@ efipart_realstrategy(void *devdata, int rw, daddr_t blk, size_t size,
/* make sure we don't read past disk end */
if ((off + size) / blkio->Media->BlockSize > d_offset + disk_blocks) {
size = d_offset + disk_blocks - off / blkio->Media->BlockSize;
diskend = d_offset + disk_blocks;
readstart = off / blkio->Media->BlockSize;
if (diskend <= readstart) {
*rsize = 0;
return (EIO);
}
size = diskend - readstart;
size = size * blkio->Media->BlockSize;
}