Frans Pop <elen...@planet.nl> writes: > On Monday 03 August 2009, Ferenc Wagner wrote: > >> I can't see anything strange in it now, but it would be interesting to >> know whether it depends on the contents of /target/etc/mtab (what if >> you delete it before the mount?). Having an strace of a second >> (successful) run might also provide a clue. > > Interesting. /target/etc/mtab does not exist yet at that point. > A 'touch /target/etc/mtab' before the chroot mount gets rid of the > segfault... > > And fun, fun, fun, after mount has segfaulted the file has magically been > created (empty), which explains why a second attempt does not segfault. > > So, what the @$#@ has changed that makes a Lenny install suddenly fail > when a Squeeze D-I is used instead of a Lenny D-I?
The two traces are very similar indeed. What I could spot: * /target vs. /target/ on the command line. * The new chroot binary reads 4 bytes from urandom and does an extra mprotect before chrooting; the old one does not. I don't know what it is, maybe an extra tripwire which (the new?) mount manages to trip, or some new type of randomization which mount isn't prepared for... Just guessing. * The new fstab is 841 bytes, the old is 492. * The new mount does some prctl trickery, and in general starts to do very different things (reads /etc/blkid.tab, /proc/whatever) just before segfaulting. Maybe it tries to use UUID-s or labels to achieve device persistence, and makes an invalid memory access analyzing the data. See for yourself like this: $ diff -u <(sed 's/[^a-z]*//i;s/0x[0-9a-f]*/ADDR/g;s/10914/PID/g;/^read(/s/".*"/STRING/' chroot.strace) <(sed 's/[^a-z]*//i;s/0x[0-9a-f]*/ADDR/g;s/13894/PID/g;/^read(/s/".*"/STRING/' chroot_lenny.strace) | less All in all it looks like some of the above reveal a bug in mount. The segfault does not come from the kernel, but from application code, as I see it. -- Good luck, Feri. -- To UNSUBSCRIBE, email to debian-boot-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
