chris@umcp-cs.UUCP (Chris Torek) (10/22/84)
Index: etc/fsck 4.2BSD Fix
Description:
Under certain uncommon conditions, fsck will die with a
segmentation fault instead of repairing a damaged file
system. The reason is that in order to calculate the number
of disk blocks used by any particular inode, one must round
up. This is done by the ``howmany'' macro as follows:
#define howmany(x, y) (((x)+((y)-1))/(y))
if x is sufficiently large, then adding y-1 may make it
negative. This is precisely what happens to fsck.
Repeat-By:
Create a file system error such that an inode has a di_size
of 0x7fffffff (or something very close to but not greater
than that), and run ``fsck'' on that file system.
Fix:
Replace the test for negative sizes with a test for either
a negative size or one that is too large:
RCS file: RCS/fsck.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -r1.1 -r1.2
620c620,621
< if (dp->di_size < 0) {
---
> if (dp->di_size < 0 ||
> dp->di_size + sblock.fs_bsize - 1 < 0) {
(For those of you who need context, this is right above an
if (debug) printf() line that prints a message about a bad
size. Or you can just search for di_size ... there's only
the one nearby.)
--
(This mind accidently left blank.)
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (301) 454-7690
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