On Mon, Apr 21, 2014 at 9:30 AM, Al Viro <v...@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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