>Synopsis: reorder_kernel generates corrupted /bsd when /usr is full
>Category: system
>Environment:
System : OpenBSD 7.7
Details : OpenBSD 7.7 (GENERIC) #619: Sun Apr 13 08:19:34 MDT 2025
[email protected]:/usr/src/sys/arch/amd64/compile/GENERIC
Architecture: OpenBSD.amd64
Machine : amd64
>Description:
If /usr is nearly full, /usr/libexec/reorder_kernel will complete
without
error, but generate a corrupted kernel which is moved into /bsd. This
will result in an unbootable system on the next boot.
>How-To-Repeat:
1. assess free space in /usr
2. subtract a few MB, dd if=/dev/zero of=/usr/foo bs=1m count=<xxx>
3. reboot so reorder_kernel will run
4. the following message will echo to console during the reorder:
uvn_flush: obj=<address>, offset=<address>. error during pageout.
uvn_flush: WARNING: changes to page may be lost!
5. note the reorder completes, filesize of /bsd will be less than
expected
the correct hash for bad /bsd has been written to
/var/db/kernel.SHA256
contents of relink.log for a corrupted/truncated kernel:
(SHA256) /bsd: OK
LD="ld" sh makegap.sh 0xcccccccc gapdummy.o
ld -T ld.script -X --warn-common -nopie -o newbsd ${SYSTEM_HEAD}
vers.o ${OBJS}
text data bss dec hex
26728562 488512 1351680 28568754 1b3ecb2
mv newbsd newbsd.gdb
ctfstrip -S -o newbsd newbsd.gdb
rm -f bsd.gdb
mv -f newbsd bsd
install -F -m 700 bsd /bsd && sha256 -h /var/db/kernel.SHA256 /bsd
Kernel has been relinked and is active on next reboot.
SHA256 (/bsd) =
75600b28045794fa983d0823435c3a07c276b13dbbf11dc01dca71a2d4fe8d6d
6. reboot
7. system will not boot. you must boot into bsd.rd to remove offending
kernel.
>Fix:
Unknown. Workaround is to disable kernel reordering or ensure
enough free space in /usr for reorder_kernel to complete successfully.
