Sukadev Bhattiprolu <[email protected]> writes:
> Sukadev Bhattiprolu [[email protected]] wrote:
> | Eric W. Biederman [[email protected]] wrote:
> | | > Anyway, is RESERVED_PIDS meant for initial kernel-threads/daemons - if
> so
> | | > would it be ok enforce it only in init_pid_ns ?
> | |
> | | It is mean for initial user space daemons, things that start on boot.
> | |
> | | I don't know how much the protection matters at this date, but we have it.
> |
> | Well, since it is not security or other critical restriction, can we allow
> | set_pidmap() a free hand - even in init-pid-ns ? It could prevent a simple
> | subtree C/R of one of the early daemons for debug for instance.
>
> So here is how I have it at present. I would like to remove the RESERVED_PIDS
> check in set_pidmap() if its ok to do so.
>
> alloc_pid() does this:
>
> if (target_pids)
> set_pidmap(tmp, target_pids[i])
> else
> alloc_pidmap(tmp);
>
> Sukadev
> ---
>
>>From bc6093fc4fc2f01070647df6f1e85e45edc89d27 Mon Sep 17 00:00:00 2001
> From: Sukadev Bhattiprolu <s...@suka.(none)>
> Date: Thu, 22 Oct 2009 16:57:28 -0700
> Subject: [PATCH] Define set_pidmap() function
>
> Define a set_pidmap() interface which is like alloc_pidmap() only that
> caller specifies the pid number to be assigned.
>
> Changelog[v9]:
> - Complete rewrite this patch based on Eric Biederman's code.
> Changelog[v7]:
> - [Eric Biederman] Generalize alloc_pidmap() to take a range of pids.
> Changelog[v6]:
> - Separate target_pid > 0 case to minimize the number of checks
> needed.
> Changelog[v3]:
> - (Eric Biederman): Avoid set_pidmap() function. Added couple of
> checks for target_pid in alloc_pidmap() itself.
> Changelog[v2]:
> - (Serge Hallyn) Check for 'pid < 0' in set_pidmap().(Code
> actually checks for 'pid <= 0' for completeness).
>
> Signed-off-by: Sukadev Bhattiprolu <[email protected]>
> ---
> kernel/pid.c | 40 ++++++++++++++++++++++++++++++++--------
> 1 files changed, 32 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/pid.c b/kernel/pid.c
> index c4d9914..9346755 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -147,18 +147,19 @@ static int alloc_pidmap_page(struct pidmap *map)
> return 0;
> }
>
> -static int alloc_pidmap(struct pid_namespace *pid_ns)
> +static int do_alloc_pidmap(struct pid_namespace *pid_ns, int last, int min,
> + int max)
> {
> - int i, offset, max_scan, pid, last = pid_ns->last_pid;
> + int i, offset, max_scan, pid;
> int rc = -EAGAIN;
> struct pidmap *map;
>
> pid = last + 1;
> if (pid >= pid_max)
> - pid = RESERVED_PIDS;
> + pid = min;
> offset = pid & BITS_PER_PAGE_MASK;
> map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
> - max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
> + max_scan = (max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
> for (i = 0; i <= max_scan; ++i) {
> rc = alloc_pidmap_page(map);
> if (rc)
> @@ -168,7 +169,6 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
> do {
> if (!test_and_set_bit(offset, map->page)) {
> atomic_dec(&map->nr_free);
> - pid_ns->last_pid = pid;
> return pid;
> }
> offset = find_next_offset(map, offset);
> @@ -179,16 +179,16 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
> * bitmap block and the final block was the same
> * as the starting point, pid is before last_pid.
> */
> - } while (offset < BITS_PER_PAGE && pid < pid_max &&
> + } while (offset < BITS_PER_PAGE && pid < max &&
> (i != max_scan || pid < last ||
> !((last+1) & BITS_PER_PAGE_MASK)));
> }
> - if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
> + if (map < &pid_ns->pidmap[(max-1)/BITS_PER_PAGE]) {
> ++map;
> offset = 0;
> } else {
> map = &pid_ns->pidmap[0];
> - offset = RESERVED_PIDS;
> + offset = min;
> if (unlikely(last == offset)) {
> rc = -EAGAIN;
> break;
> @@ -199,6 +199,30 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
> return rc;
> }
>
> +static int alloc_pidmap(struct pid_namespace *pid_ns)
> +{
> + int nr;
> +
> + nr = do_alloc_pidmap(pid_ns, pid_ns->last, RESERVED_PIDS, pid_max);
pid_ns->last_pid,
Looks like I missed that one.
> + if (nr >= 0)
> + pid_ns->last_pid = nr;
> + return nr;
> +}
> +
> +static int set_pidmap(struct pid_namespace *pid_ns, int target)
> +{
> + if (!target)
> + return alloc_pidmap(pid_ns);
> +
> + if (target >= pid_max)
> + return -EINVAL;
> +
> + if ((target < 0) || (target < RESERVED_PIDS && pid_ns == &init_pid_ns))
> + return -EINVAL;
if ((target < 0) || ((target < RESERVED_PIDS) && (pid_ns->last_pid >=
RESERVED_PIDS)))
Please.
Eric
> +
> + return do_alloc_pidmap(pid_ns, target - 1, target, target + 1);
> +}
> +
> int next_pidmap(struct pid_namespace *pid_ns, int last)
> {
> int offset;
> --
> 1.6.0.4
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