Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 21 Apr 2014 10:00:55 -0700 | Subject | Re: [RFC 2/2] fs,proc: Respect FMODE_WRITE when opening /proc/pid/fd/N |
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On Mon, Apr 21, 2014 at 9:30 AM, Al Viro <viro@zeniv.linux.org.uk> wrote: > On Mon, Apr 21, 2014 at 09:22:48AM -0700, Andy Lutomirski wrote: > >> +static int proc_may_follow(struct nameidata *nd, struct file *f) >> +{ >> + if (!nd) >> + return 0; /* This is readlink, */ >> + >> + if ((nd->flags & LOOKUP_WRITE) && !(f->f_mode & FMODE_WRITE)) >> + return -EACCES; >> + >> + return 0; >> +} > > And this is just plain wrong. WTF are you making the traversal of symlink > in the middle of pathname dependent on the open flags?
Can you give me a hint? There are three cases that I need to distinguish, I think:
1. readlink. Currently handled by nd == NULL. It's ugly, and I'll clean it up.
2. Traversal in the middle of a path. This can be either literally in the middle (e.g. "/proc/self/fd/3/something_else") or in a symlink that's the last component of the literal path (e.g. "fd3null" where "fd3null" is a symlink to "/proc/self/fd/3/null" and "null" is either a file or a symlink to /dev/null). I have the latter type wrong in this patch.
3. Actually opening /proc/self/fd/N. This can be direct or by opening a symlink to /proc/self/fd/N. I think I have this case correct.
What's the best way to fix this? Should I be checking nd->depth?
--Andy
> > NAK.
-- Andy Lutomirski AMA Capital Management, LLC
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