On 03.10.2012 13:05, Kees Cook wrote: > Hi Nick, > > 3.6 introduced link restrictions: > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=800179c9b8a1e796e441674776d11cd4c05d61d7 > > It sounds like you've got symlinks in a world-writable directory, and > you're following those symlinks across mis-matched uids. You can either > have the symlinks be owned by the directory owner, or you can turn off > symlink restrictions in sysctl: > > # echo 0 > /proc/sys/fs/protected_symlinks
According to documentation world writable isn't the problem. It's world writable inside/or below a directory with sticky bit. (Documentation/sysctl/fs.txt -> protected_symlinks) So /scratch_space must have the sticky bit set. Question is: Why? Personally i would have been bitten by this change, because for years i have used a symlink in /tmp (which has the sticky bit) to a directory somewhere else for historical reasons. But as i was aware of this change i fixed my system before booting the new kernel. > On Wed, Oct 03, 2012 at 03:46:14PM -0400, Nick Bowler wrote: > > On 2012-09-30 17:38 -0700, Linus Torvalds wrote: > > > So here it is, 3.6 final. Sure, I'd have been happier with even fewer > > > changes, but that just never happens. And holding off the release > > > until people get too bored to send me the small stuff just makes the > > > next merge window more painful. > > > > Just upgraded to 3.6 from 3.5, and now some of my kernel build scripts > > are throwing "permission denied" errors. Apparently symlinks are > > broken somehow? > > > > # id > > uid=0(root) gid=0(root) > > groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video) > > > > # ls -l /scratch_space/linux > > drwxr-xr-x 24 nbowler eng 4096 2012-10-03 13:41 /scratch_space/linux > > > > # readlink /scratch_space/linux-2.6 > > linux > > > > # cd /scratch_space/linux > > # pwd > > /scratch_space/linux > > > > # cd /scratch_space/linux-2.6 > > cd: permission denied: /scratch_space/linux-2.6 > > > > WTF? 3.5 is fine. I will try to bisect this later, but I figured I'd > > throw this out there now in case anyone has any ideas... Bis denn -- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
