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Date: Sat, 29 Oct 2016 12:19:55 -0400
From: David Windsor <dwindsor@...il.com>
To: kernel-hardening@...ts.openwall.com
Cc: keescook@...omium.org,
elena.reshetova@...el.com,
ishkamiel@...il.com,
takahiro.akashi@...aro.org,
colin@...dal.org,
dwindsor@...il.com
Subject: [RFC PATCH 4/5] fs: add overflow protection to struct pipe_inode_info.{readers|writers|files|waiting_writers}
Change type of struct pipe_inode_info.{readers|writers|files|waiting_writers} to atomic_t.
This enables overflow protection: when CONFIG_HARDENED_ATOMIC is enabled, atomic_t variables
cannot be overflowed.
The copyright for the original PAX_REFCOUNT code:
- all REFCOUNT code in general: PaX Team <pageexec@...email.hu>
- various false positive fixes: Mathias Krause <minipli@...glemail.com>
---
fs/coredump.c | 10 ++++----
fs/pipe.c | 59 ++++++++++++++++++++++++-----------------------
fs/splice.c | 36 ++++++++++++++---------------
include/linux/pipe_fs_i.h | 8 +++----
4 files changed, 57 insertions(+), 56 deletions(-)
diff --git a/fs/coredump.c b/fs/coredump.c
index 8d323b4..4ae7b89 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -483,8 +483,8 @@ static void wait_for_dump_helpers(struct file *file)
struct pipe_inode_info *pipe = file->private_data;
pipe_lock(pipe);
- pipe->readers++;
- pipe->writers--;
+ atomic_inc(&pipe->readers);
+ atomic_dec(&pipe->writers);
wake_up_interruptible_sync(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
pipe_unlock(pipe);
@@ -493,11 +493,11 @@ static void wait_for_dump_helpers(struct file *file)
* We actually want wait_event_freezable() but then we need
* to clear TIF_SIGPENDING and improve dump_interrupted().
*/
- wait_event_interruptible(pipe->wait, pipe->readers == 1);
+ wait_event_interruptible(pipe->wait, atomic_read(&pipe->readers) == 1);
pipe_lock(pipe);
- pipe->readers--;
- pipe->writers++;
+ atomic_dec(&pipe->readers);
+ atomic_inc(&pipe->writers);
pipe_unlock(pipe);
}
diff --git a/fs/pipe.c b/fs/pipe.c
index 8e0d9f2..ceea372 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -62,7 +62,7 @@ unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
{
- if (pipe->files)
+ if (atomic_read(&pipe->files))
mutex_lock_nested(&pipe->mutex, subclass);
}
@@ -77,7 +77,7 @@ EXPORT_SYMBOL(pipe_lock);
void pipe_unlock(struct pipe_inode_info *pipe)
{
- if (pipe->files)
+ if (atomic_read(&pipe->files))
mutex_unlock(&pipe->mutex);
}
EXPORT_SYMBOL(pipe_unlock);
@@ -310,9 +310,9 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
}
if (bufs) /* More to do? */
continue;
- if (!pipe->writers)
+ if (!atomic_read(&pipe->writers))
break;
- if (!pipe->waiting_writers) {
+ if (!atomic_read(&pipe->waiting_writers)) {
/* syscall merging: Usually we must not sleep
* if O_NONBLOCK is set, or if we got some data.
* But if a writer sleeps in kernel space, then
@@ -369,7 +369,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
__pipe_lock(pipe);
- if (!pipe->readers) {
+ if (!atomic_read(&pipe->readers)) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
goto out;
@@ -403,7 +403,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
for (;;) {
int bufs;
- if (!pipe->readers) {
+ if (!atomic_read(&pipe->readers)) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
@@ -471,9 +471,9 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
do_wakeup = 0;
}
- pipe->waiting_writers++;
+ atomic_inc(&pipe->waiting_writers);
pipe_wait(pipe);
- pipe->waiting_writers--;
+ atomic_dec(&pipe->waiting_writers);
}
out:
__pipe_unlock(pipe);
@@ -528,7 +528,7 @@ pipe_poll(struct file *filp, poll_table *wait)
mask = 0;
if (filp->f_mode & FMODE_READ) {
mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
- if (!pipe->writers && filp->f_version != pipe->w_counter)
+ if (!atomic_read(&pipe->writers) && filp->f_version != pipe->w_counter)
mask |= POLLHUP;
}
@@ -538,7 +538,7 @@ pipe_poll(struct file *filp, poll_table *wait)
* Most Unices do not set POLLERR for FIFOs but on Linux they
* behave exactly like pipes for poll().
*/
- if (!pipe->readers)
+ if (!atomic_read(&pipe->readers))
mask |= POLLERR;
}
@@ -550,7 +550,7 @@ static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
int kill = 0;
spin_lock(&inode->i_lock);
- if (!--pipe->files) {
+ if (atomic_dec_and_test(&pipe->files)) {
inode->i_pipe = NULL;
kill = 1;
}
@@ -567,11 +567,11 @@ pipe_release(struct inode *inode, struct file *file)
__pipe_lock(pipe);
if (file->f_mode & FMODE_READ)
- pipe->readers--;
+ atomic_dec(&pipe->readers);
if (file->f_mode & FMODE_WRITE)
- pipe->writers--;
+ atomic_dec(&pipe->writers);
- if (pipe->readers || pipe->writers) {
+ if (atomic_read(&pipe->readers) || atomic_read(&pipe->writers)) {
wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
@@ -708,8 +708,9 @@ static struct inode * get_pipe_inode(void)
goto fail_iput;
inode->i_pipe = pipe;
- pipe->files = 2;
- pipe->readers = pipe->writers = 1;
+ atomic_set(&pipe->files, 2);
+ atomic_set(&pipe->readers, 1);
+ atomic_set(&pipe->writers, 1);
inode->i_fop = &pipefifo_fops;
/*
@@ -891,17 +892,17 @@ static int fifo_open(struct inode *inode, struct file *filp)
spin_lock(&inode->i_lock);
if (inode->i_pipe) {
pipe = inode->i_pipe;
- pipe->files++;
+ atomic_inc(&pipe->files);
spin_unlock(&inode->i_lock);
} else {
spin_unlock(&inode->i_lock);
pipe = alloc_pipe_info();
if (!pipe)
return -ENOMEM;
- pipe->files = 1;
+ atomic_set(&pipe->files, 1);
spin_lock(&inode->i_lock);
if (unlikely(inode->i_pipe)) {
- inode->i_pipe->files++;
+ atomic_inc(&inode->i_pipe->files);
spin_unlock(&inode->i_lock);
free_pipe_info(pipe);
pipe = inode->i_pipe;
@@ -926,10 +927,10 @@ static int fifo_open(struct inode *inode, struct file *filp)
* opened, even when there is no process writing the FIFO.
*/
pipe->r_counter++;
- if (pipe->readers++ == 0)
+ if (atomic_inc_return(&pipe->readers) == 1)
wake_up_partner(pipe);
- if (!is_pipe && !pipe->writers) {
+ if (!is_pipe && !atomic_read(&pipe->writers)) {
if ((filp->f_flags & O_NONBLOCK)) {
/* suppress POLLHUP until we have
* seen a writer */
@@ -948,14 +949,14 @@ static int fifo_open(struct inode *inode, struct file *filp)
* errno=ENXIO when there is no process reading the FIFO.
*/
ret = -ENXIO;
- if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
+ if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !atomic_read(&pipe->readers))
goto err;
pipe->w_counter++;
- if (!pipe->writers++)
+ if (atomic_inc_return(&pipe->writers) == 1)
wake_up_partner(pipe);
- if (!is_pipe && !pipe->readers) {
+ if (!is_pipe && !atomic_read(&pipe->readers)) {
if (wait_for_partner(pipe, &pipe->r_counter))
goto err_wr;
}
@@ -969,11 +970,11 @@ static int fifo_open(struct inode *inode, struct file *filp)
* the process can at least talk to itself.
*/
- pipe->readers++;
- pipe->writers++;
+ atomic_read(&pipe->readers);
+ atomic_inc(&pipe->writers);
pipe->r_counter++;
pipe->w_counter++;
- if (pipe->readers == 1 || pipe->writers == 1)
+ if (atomic_read(&pipe->readers) == 1 || atomic_read(&pipe->writers) == 1)
wake_up_partner(pipe);
break;
@@ -987,13 +988,13 @@ static int fifo_open(struct inode *inode, struct file *filp)
return 0;
err_rd:
- if (!--pipe->readers)
+ if (atomic_dec_and_test(&pipe->readers))
wake_up_interruptible(&pipe->wait);
ret = -ERESTARTSYS;
goto err;
err_wr:
- if (!--pipe->writers)
+ if (atomic_dec_and_test(&pipe->writers))
wake_up_interruptible(&pipe->wait);
ret = -ERESTARTSYS;
goto err;
diff --git a/fs/splice.c b/fs/splice.c
index 153d4f3..8376baa 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -188,7 +188,7 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
if (!spd_pages)
return 0;
- if (unlikely(!pipe->readers)) {
+ if (unlikely(!atomic_read(&pipe->readers))) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
goto out;
@@ -227,7 +227,7 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
int ret;
- if (unlikely(!pipe->readers)) {
+ if (unlikely(!atomic_read(&pipe->readers))) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
} else if (pipe->nrbufs == pipe->buffers) {
@@ -537,7 +537,7 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des
pipe_buf_release(pipe, buf);
pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
pipe->nrbufs--;
- if (pipe->files)
+ if (atomic_read(&pipe->files))
sd->need_wakeup = true;
}
@@ -568,10 +568,10 @@ static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_des
return -ERESTARTSYS;
while (!pipe->nrbufs) {
- if (!pipe->writers)
+ if (!atomic_read(&pipe->writers))
return 0;
- if (!pipe->waiting_writers && sd->num_spliced)
+ if (!atomic_read(&pipe->waiting_writers) && sd->num_spliced)
return 0;
if (sd->flags & SPLICE_F_NONBLOCK)
@@ -785,7 +785,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
pipe_buf_release(pipe, buf);
pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
pipe->nrbufs--;
- if (pipe->files)
+ if (atomic_read(&pipe->files))
sd.need_wakeup = true;
} else {
buf->offset += ret;
@@ -948,7 +948,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
* out of the pipe right after the splice_to_pipe(). So set
* PIPE_READERS appropriately.
*/
- pipe->readers = 1;
+ atomic_set(&pipe->readers, 1);
current->splice_pipe = pipe;
}
@@ -1095,9 +1095,9 @@ static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
return -EAGAIN;
if (signal_pending(current))
return -ERESTARTSYS;
- pipe->waiting_writers++;
+ atomic_inc(&pipe->waiting_writers);
pipe_wait(pipe);
- pipe->waiting_writers--;
+ atomic_dec(&pipe->waiting_writers);
}
return 0;
}
@@ -1445,9 +1445,9 @@ static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
ret = -ERESTARTSYS;
break;
}
- if (!pipe->writers)
+ if (!atomic_read(&pipe->writers))
break;
- if (!pipe->waiting_writers) {
+ if (!atomic_read(&pipe->waiting_writers)) {
if (flags & SPLICE_F_NONBLOCK) {
ret = -EAGAIN;
break;
@@ -1479,7 +1479,7 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
pipe_lock(pipe);
while (pipe->nrbufs >= pipe->buffers) {
- if (!pipe->readers) {
+ if (!atomic_read(&pipe->readers)) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
break;
@@ -1492,9 +1492,9 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
ret = -ERESTARTSYS;
break;
}
- pipe->waiting_writers++;
+ atomic_inc(&pipe->waiting_writers);
pipe_wait(pipe);
- pipe->waiting_writers--;
+ atomic_dec(&pipe->waiting_writers);
}
pipe_unlock(pipe);
@@ -1530,14 +1530,14 @@ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
pipe_double_lock(ipipe, opipe);
do {
- if (!opipe->readers) {
+ if (!atomic_read(&opipe->readers)) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
- if (!ipipe->nrbufs && !ipipe->writers)
+ if (!ipipe->nrbufs && !atomic_read(&ipipe->writers))
break;
/*
@@ -1634,7 +1634,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
pipe_double_lock(ipipe, opipe);
do {
- if (!opipe->readers) {
+ if (!atomic_read(&opipe->readers)) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
@@ -1679,7 +1679,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
* return EAGAIN if we have the potential of some data in the
* future, otherwise just return 0
*/
- if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
+ if (!ret && atomic_read(&ipipe->waiting_writers) && (flags & SPLICE_F_NONBLOCK))
ret = -EAGAIN;
pipe_unlock(ipipe);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index e7497c9..43ebf07 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -48,10 +48,10 @@ struct pipe_inode_info {
struct mutex mutex;
wait_queue_head_t wait;
unsigned int nrbufs, curbuf, buffers;
- unsigned int readers;
- unsigned int writers;
- unsigned int files;
- unsigned int waiting_writers;
+ atomic_t readers;
+ atomic_t writers;
+ atomic_t files;
+ atomic_t waiting_writers;
unsigned int r_counter;
unsigned int w_counter;
struct page *tmp_page;
--
2.7.4
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