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Date: Thu, 4 May 2017 20:46:49 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Jann Horn <jannh@...gle.com> Cc: Al Viro <viro@...iv.linux.org.uk>, Linux API <linux-api@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, David Drysdale <drysdale@...gle.com> Subject: Re: new ...at() flag: AT_NO_JUMPS On Thu, May 4, 2017 at 7:47 PM, Jann Horn <jannh@...gle.com> wrote: > > Thread 1 starts an AT_BENEATH path walk using an O_PATH fd > pointing to /srv/www/example.org/foo; the path given to the syscall is > "bar/../../../../etc/passwd". The path walk enters the "bar" directory. > Thread 2 moves /srv/www/example.org/foo/bar to > /srv/www/example.org/bar. > Thread 1 processes the rest of the path ("../../../../etc/passwd"), never > hitting /srv/www/example.org/foo in the process. > > I'm not really familiar with the VFS internals, but from a coarse look > at the patch, it seems like it wouldn't block this? I think you're right. I guess it would be safe for the RCU case due to the sequence number check, but not the non-RCU case. Al? Linus
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