On Thu, 31 Mar 2005, Colin Percival wrote:
Tom Alsberg wrote:
Perhaps this should go to -STABLE, I just couldn't be sure.
It will get more attention on freebsd-stable@, so I'm CCing that list.
We are trying out FreeBSD 5.4-PRERELEASE on diskless clients. I
noticed one problem, being that when setting the LD_LIBRARY_PATH
(or for that matter, LD_PRELOAD, and LD_LIBMAP_DISABLE) environment
variables, nothing will run, as /libexec/ld-elf.so.1 complains:
Cannot execute objects on /
According to the sources, this was added in 5.4, and will happen
if / is mounted noexec.
Yes, that's quite correct -- although I can't imagine how a bug which
caused / to be labelled as noexec managed to avoid causing major
problems until now.
I don't know anything about NFS, but hopefully someone on -stable
will be able to work out what's going on from the rest of your
email (quoted below).
Colin Percival
In this case, / is mounted by the BTX PXE loader over NFS (from a
FreeBSD 5.3 server, right now). mount does not show the noexec
flag. However, with the attached little C program I verified that
statfs really returns this flag (0x0006).
Now, I see that on FreeBSD 5.3 diskless clients this flag is also
returned on / - just it happened that nobody looked at it until
the change in rtld.c of FreeBSD 5.4:
if (fs.f_flags MNT_NOEXEC) {
_rtld_error(Cannot execute objects on %s\n, fs.f_mntonname);
close(fd);
return NULL;
}
I didn't yet understand (didn't check much) - why does statfs report
the MNT_NOEXEC flag on the / filesystem (and only the / filesystem,
when it's mounted from NFS by the bootloader - not any other
NFS filesystems)? BTW, this happens also with NetApp as the NFS
server - just to rule out any possibility of relation here.
Ideas appreciated,
-- Tom
#include stdio.h
#include fcntl.h
#include sys/param.h
#include sys/mount.h
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, invalid number of arguments);
return -1;
}
struct statfs stbuf;
if (statfs(argv[1], stbuf) != 0) {
perror(fstatfs);
return -1;
}
printf(FLAGS: 0x%08X\n, stbuf.f_flags);
if (stbuf.f_flags MNT_NOEXEC)
printf(MNT_NOEXEC\n);
return 0;
}
I've managed to reproduce this with a simple:
www1# gcc -o noexec noexec.c
www1# umount /buildroot/
www1# mount nfs3:/export/vol1/build/BUILDROOT-WWW /buildroot
www1# ./noexec /buildroot/
exec
www1# umount /buildroot/
www1# mount -o -r=32768 nfs3:/export/vol1/build/BUILDROOT-WWW /buildroot
www1# ./noexec /buildroot/
noexec
www1#
Pretty funky shit this :).
PR: 85268
http://www.freebsd.org/cgi/query-pr.cgi?pr=85268
Anybody care to take a deeper look ?
--
Sten Spans
There is a crack in everything, that's how the light gets in.
Leonard Cohen - Anthem
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