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USB: fix race leading to a write after kfree in usbfs

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this fixes a race between async_completed() and proc_reapurbnonblock().

CPU A                   CPU B

spin_lock(&ps->lock);
list_move_tail(&as->asynclist, &ps->async_completed);
spin_unlock(&ps->lock);

                                if (!(as = async_getcompleted(ps)))
                                        return -EAGAIN;
                                return processcompl(as, (void __user * __user *)arg);

processcompl() calls free_async() which calls kfree(as)

as->status = urb->status;
if (as->signr) {
        sinfo.si_signo = as->signr;
        sinfo.si_errno = as->status;
        sinfo.si_code = SI_ASYNCIO;
        sinfo.si_addr = as->userurb;
        kill_pid_info_as_uid(as->signr, &sinfo, as->pid, as->uid,
                              as->euid, as->secid);
}
snoop(&urb->dev->dev, "urb complete\n");
snoop_urb(urb, as->userurb);

write after kfree

Signed-off-by: Oliver Neukum <oliver@neukum.org>
This commit is contained in:
Oliver Neukum 2009-07-08 19:09:23 +02:00 committed by Greg Kroah-Hartman
parent 7bae0a070d
commit 516a1a07f0
1 changed files with 17 additions and 4 deletions
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21
drivers/usb/core/devio.c
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@ -325,21 +325,34 @@ static void async_completed(struct urb *urb)
struct async *as = urb->context;
struct dev_state *ps = as->ps;
struct siginfo sinfo;
struct pid *pid = NULL;
uid_t uid = 0;
uid_t euid = 0;
u32 secid = 0;
int signr;
spin_lock(&ps->lock);
list_move_tail(&as->asynclist, &ps->async_completed);
spin_unlock(&ps->lock);
as->status = urb->status;
if (as->signr) {
signr = as->signr;
if (signr) {
sinfo.si_signo = as->signr;
sinfo.si_errno = as->status;
sinfo.si_code = SI_ASYNCIO;
sinfo.si_addr = as->userurb;
kill_pid_info_as_uid(as->signr, &sinfo, as->pid, as->uid,
as->euid, as->secid);
pid = as->pid;
uid = as->uid;
euid = as->euid;
secid = as->secid;
}
snoop(&urb->dev->dev, "urb complete\n");
snoop_urb(urb, as->userurb);
spin_unlock(&ps->lock);
if (signr)
kill_pid_info_as_uid(sinfo.si_signo, &sinfo, pid, uid,
euid, secid);
wake_up(&ps->wait);
}