> On Tue, Aug 19, 2008 at 11:13:39AM +0200, Jan Kara wrote: > > > Isn't equivalent checking done in ext2_check_descriptors()? It would make > > > sense to abstract out the "check one group and return error" code and use > > > it in both places. > > Actually yes, it is. Good point. Sami, is it the case that you have > > mounted the filesystem, then intentionally corrupted it and after that > > the kernel oopsed (as opposed to first corrupting the filesystem image and > > mounting it after that)? That would explain how corrupted values could get > > to read_block_bitmap() even though ext2_check_descriptors() checked them. > > No, that's not what I do. I corrupt the fs before mounting it, then > mount it, perform normal filesystem operations on it and unmount it. OK, thanks. Then we must somehow corrupt group descriptor block during the operation. Because I'm pretty sure it *is* corrupted - the oops is: unable to handle kernel paging request at c7e95ffc. If we look into registers, we see ECX has c7e96000 (which is probably bh->b_data). In the second oops it's exactly the same - ECX has c11e4000, the oops is at address c11e3ffc. So in both cases it is ECX-4. So somehow we managed to pass negative offset into ext2_test_bit(). But as Andreas pointed out, when we load descriptors into memory, we check that both bitmaps and inode table is in ext2_check_descriptors()... The other possibility would be that we managed to corrupts s_first_data_block in the superblock. Anyway, both possibilities don't look very likely. I'll try to reproduce the problem and maybe get more insight... How large is your filesystem BTW? > Here's the most current script I use (zzuf is the fuzzer): > > ------------------------------------------------------------ > #!/bin/sh > > if [ "`hostname`" != "fstest" ]; then > echo "This is a dangerous script." > echo "Set your hostname to \`fstest\' if you want to use it." > exit 1 > fi > > umount /dev/hdb > umount /dev/hdc > /etc/init.d/sysklogd stop > /etc/init.d/klogd stop > /etc/init.d/cron stop > mount /dev/hda / -t ext3 -o remount,ro || exit 1 > > #ulimit -t 20 > > for ((s=$1; s<1000000000; s++)); do > umount /mnt > echo '***** zzuffing *****' seed $s > zzuf -r 0:0.03 -s $s </dev/hdc >/dev/hdb || exit > mount /dev/hdb /mnt -t ext2 -o errors=continue || continue > cd /mnt || continue > timeout 30 cp -r doc doc2 >&/dev/null > timeout 30 find -xdev >&/dev/null > timeout 30 find -xdev -print0 2>/dev/null |xargs -0 touch -- 2>/dev/null > timeout 30 mkdir tmp >&/dev/null > timeout 30 echo whoah >tmp/filu 2>/dev/null > timeout 30 rm -rf /mnt/* >&/dev/null > cd / > done > ------------------------------------------------------------ Honza -- Jan Kara <jack@xxxxxxx> SuSE CR Labs -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
