fs,proc: Respect FMODE_WRITE when opening /proc/pid/fd/N
This patch does this:
# (echo asdf >/proc/self/fd/3) 3</dev/null
bash: /proc/self/fd/3: Permission denied
I'm not confident that my use of nd->flags is correct. I'm also not
confident that this hooks in to path lookup in the right place.
It is not complete. It doesn't handle FMODE_READ. It also doesn't
handle FMODE_EXEC or FMODE_PATH, but the desired semantics there are
less clear. For example, this should probably continue to work:
(/proc/self/fd/3 Hello) 3</bin/echo
This patch does not do anything to /proc/self/exe. It probably should.
This may break userspace. If so, I would argue that anything broken
by it is either an actual exploit or is so broken that it doesn't
deserve to continue working. If it breaks something important, then
maybe it will need a sysctl.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
3 files changed
