On Tue, 15 Oct 2002, Poul-Henning Kamp wrote:
In message [EMAIL PROTECTED], Nate Lawson wri
tes:
fdisk against my USB flash drive crashes with divide by zero. It turns
out that get_params() starts with some default values (since there is
no disklabel) and then runs some ioctls: DIOCGFWSECTORS and DIOCGFWHEADS.
The problem is that fdisk checks the error from that ioctl and then
happily uses whatever parameters it returned. My question is, should I
add the error checking in userland (error == 0 sector != 0) or in
g_dev_ioctl? IMO, it should be in g_dev_ioctl so that we only have to
validate the data in one place instead of multiple utilities (fdisk,
disklabel, ...?)
I really think it belongs in userland and not in the kernel.
The FW values are advisory, and if they are not there or not
sensible, userland should cope.
I could agree to make g_dev_ioctl fail the ioctl with some errno
if they came back as zero, but not substituting another value.
The attached patch makes everything work fine for my drive (64 MB USB
flash).
-Nate
fdisk: can't get disk parameters on /dev/da0; supplying dummy ones
*** Working on device /dev/da0 ***
parameters extracted from in-core disklabel are:
cylinders=129024 heads=1 sectors/track=1 (1 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=129024 heads=1 sectors/track=1 (1 blks/cyl)
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 6 (0x06),(Primary 'big' DOS (= 32MB))
start 32, size 128480 (62 Meg), flag 80 (active)
beg: cyl 0/ head 1/ sector 1;
end: cyl 250/ head 15/ sector 32
The data for partition 2 is:
UNUSED
The data for partition 3 is:
UNUSED
The data for partition 4 is:
UNUSED
Index: sys/geom/geom_dev.c
===
RCS file: /home/ncvs/src/sys/geom/geom_dev.c,v
retrieving revision 1.25
diff -u -r1.25 geom_dev.c
--- sys/geom/geom_dev.c 7 Oct 2002 06:25:26 - 1.25
+++ sys/geom/geom_dev.c 15 Oct 2002 12:46:35 -
@@ -245,15 +245,23 @@
switch (cmd) {
case DIOCGSECTORSIZE:
error = g_io_getattr(GEOM::sectorsize, cp, i, data);
+ if (error == 0 *(u_int *)data == 0)
+ error = EINVAL;
break;
case DIOCGMEDIASIZE:
error = g_io_getattr(GEOM::mediasize, cp, i, data);
+ if (error == 0 *(u_int *)data == 0)
+ error = EINVAL;
break;
case DIOCGFWSECTORS:
error = g_io_getattr(GEOM::fwsectors, cp, i, data);
+ if (error == 0 *(u_int *)data == 0)
+ error = EINVAL;
break;
case DIOCGFWHEADS:
error = g_io_getattr(GEOM::fwheads, cp, i, data);
+ if (error == 0 *(u_int *)data == 0)
+ error = EINVAL;
break;
case DIOCGFRONTSTUFF:
error = g_io_getattr(GEOM::frontstuff, cp, i, data);
