4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric W. Biederman ebiederm@xmission.com
commit 0ab93e9c99f8208c0a1a7b7170c827936268c996 upstream.
The genweq_add_file and genwqe_del_file by caching current without using reference counting embed the assumption that a file descriptor will never be passed from one process to another. It even embeds the assumption that the the thread that opened the file will be in existence when the process terminates. Neither of which are guaranteed to be true.
Therefore replace caching the task_struct of the opener with pid of the openers thread group id. All the knowledge of the opener is used for is as the target of SIGKILL and a SIGKILL will kill the entire process group.
Rename genwqe_force_sig to genwqe_terminate, remove it's unncessary signal argument, update it's ownly caller, and use kill_pid instead of force_sig.
The work force_sig does in changing signal handling state is not relevant to SIGKILL sent as SEND_SIG_PRIV. The exact same processess will be killed just with less work, and less confusion. The work done by force_sig is really only needed for handling syncrhonous exceptions.
It will still be possible to cause genwqe_device_remove to wait 8 seconds by passing a file descriptor to another process but the possible user after free is fixed.
Fixes: eaf4722d4645 ("GenWQE Character device and DDCB queue") Cc: stable@vger.kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Frank Haverkamp haver@linux.vnet.ibm.com Cc: Joerg-Stephan Vogt jsvogt@de.ibm.com Cc: Michael Jung mijung@gmx.net Cc: Michael Ruettger michael@ibmra.de Cc: Kleber Sacilotto de Souza klebers@linux.vnet.ibm.com Cc: Sebastian Ott sebott@linux.vnet.ibm.com Cc: Eberhard S. Amann esa@linux.vnet.ibm.com Cc: Gabriel Krisman Bertazi krisman@linux.vnet.ibm.com Cc: Guilherme G. Piccoli gpiccoli@linux.vnet.ibm.com Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/misc/genwqe/card_base.h | 2 +- drivers/misc/genwqe/card_dev.c | 9 +++++---- 2 files changed, 6 insertions(+), 5 deletions(-)
--- a/drivers/misc/genwqe/card_base.h +++ b/drivers/misc/genwqe/card_base.h @@ -408,7 +408,7 @@ struct genwqe_file { struct file *filp;
struct fasync_struct *async_queue; - struct task_struct *owner; + struct pid *opener; struct list_head list; /* entry in list of open files */
spinlock_t map_lock; /* lock for dma_mappings */ --- a/drivers/misc/genwqe/card_dev.c +++ b/drivers/misc/genwqe/card_dev.c @@ -52,7 +52,7 @@ static void genwqe_add_file(struct genwq { unsigned long flags;
- cfile->owner = current; + cfile->opener = get_pid(task_tgid(current)); spin_lock_irqsave(&cd->file_lock, flags); list_add(&cfile->list, &cd->file_list); spin_unlock_irqrestore(&cd->file_lock, flags); @@ -65,6 +65,7 @@ static int genwqe_del_file(struct genwqe spin_lock_irqsave(&cd->file_lock, flags); list_del(&cfile->list); spin_unlock_irqrestore(&cd->file_lock, flags); + put_pid(cfile->opener);
return 0; } @@ -275,7 +276,7 @@ static int genwqe_kill_fasync(struct gen return files; }
-static int genwqe_force_sig(struct genwqe_dev *cd, int sig) +static int genwqe_terminate(struct genwqe_dev *cd) { unsigned int files = 0; unsigned long flags; @@ -283,7 +284,7 @@ static int genwqe_force_sig(struct genwq
spin_lock_irqsave(&cd->file_lock, flags); list_for_each_entry(cfile, &cd->file_list, list) { - force_sig(sig, cfile->owner); + kill_pid(cfile->opener, SIGKILL, 1); files++; } spin_unlock_irqrestore(&cd->file_lock, flags); @@ -1357,7 +1358,7 @@ static int genwqe_inform_and_stop_proces dev_warn(&pci_dev->dev, "[%s] send SIGKILL and wait ...\n", __func__);
- rc = genwqe_force_sig(cd, SIGKILL); /* force terminate */ + rc = genwqe_terminate(cd); if (rc) { /* Give kill_timout more seconds to end processes */ for (i = 0; (i < GENWQE_KILL_TIMEOUT) &&