From 516a1a07f0219d6672fb6b8e49fb9d5d533c2e89 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Wed, 8 Jul 2009 19:09:23 +0200 Subject: [PATCH] USB: fix race leading to a write after kfree in usbfs 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 --- drivers/usb/core/devio.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index 706f181..46ca2af 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -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); } -- 1.8.2.3