Messages in this thread | | | Date | Tue, 29 Jun 2010 08:09:52 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] sanitize task->comm to avoid leaking escape codes |
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On Tue, Jun 29, 2010 at 11:45:14AM +0300, Alexey Dobriyan wrote: > On Tue, Jun 29, 2010 at 12:03 AM, Kees Cook <kees.cook@canonical.com> wrote: > > On Mon, Jun 28, 2010 at 01:00:28PM -0700, Andrew Morton wrote: > >> Surely it would be better to fix the tools which display this info > >> rather than making the kernel tell fibs. > > > > The strncpy in get_task_comm() is totally wrong -- it's testing the length > > of task->comm. > > It also fills not just any buffer but buffer which is TASK_COMM_LEN byte wide. > > > Why should get_task_comm not take a destination buffer length argument? > > If you pass too small, you needlessly truncate output.
If you pass too small a buffer, get_task_comm will happily write all over the caller's stack past the end of the buffer if the contents of task->comm are large enough:
strncpy(buf, tsk->comm, sizeof(tsk->comm));
The "n" argument to get_task_comm's use of strncpy is totally wrong -- it needs to be the size of the destination, not the size of the source. Luckily, everyone using get_task_comm currently uses buffers that are sizeof(task->comm).
> If you pass too large, you waste space.
Right.
-Kees
-- Kees Cook Ubuntu Security Team
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