[media] saa7164: add guard bytes around critical buffers to detect failure

If the guard bytes are trampled then we have a memory related problem.

Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 37 insertions, 6 deletions

diff --git a/drivers/media/video/saa7164/saa7164-core.c b/drivers/media/video/saa7164/saa7164-core.c
index 624ad3e1b61..e96bbe4698b 100644
--- a/drivers/media/video/saa7164/saa7164-core.c
+++ b/drivers/media/video/saa7164/saa7164-core.c
@@ -216,6 +216,7 @@ static void saa7164_work_enchandler(struct work_struct *w)
         struct saa7164_user_buffer *ubuf;
         struct list_head *c, *n;
         int wp, rp, i = 0;
+        u8 *p;
 
         port->last_svc_msecs_diff = port->last_svc_msecs;
         port->last_svc_msecs = jiffies_to_msecs(jiffies);
@@ -262,6 +263,20 @@ static void saa7164_work_enchandler(struct work_struct *w)
                         break;
                 }
 
+                p = (u8 *)buf->cpu;
+                if (    (*(p + buf->actual_size + 0) != 0xff) ||
+                        (*(p + buf->actual_size + 1) != 0xff) ||
+                        (*(p + buf->actual_size + 2) != 0xff) ||
+                        (*(p + buf->actual_size + 3) != 0xff) ||
+                        (*(p + buf->actual_size + 0x10) != 0xff) ||
+                        (*(p + buf->actual_size + 0x11) != 0xff) ||
+                        (*(p + buf->actual_size + 0x12) != 0xff) ||
+                        (*(p + buf->actual_size + 0x13) != 0xff) )
+                {
+                        printk(KERN_ERR "buf %p failed guard check\n", buf);
+                        saa7164_dumphex16(dev, p + buf->actual_size - 32, 64);
+                }
+
                 if (buf->idx == rp) {
                         /* Found the buffer, deal with it */
                         dprintk(DBGLVL_IRQ, "%s() wp: %d processing: %d\n",
@@ -278,9 +293,12 @@ static void saa7164_work_enchandler(struct work_struct *w)
                                 ubuf = list_first_entry(&port->list_buf_free.list,
                                         struct saa7164_user_buffer, list);
 
-                                if (ubuf->actual_size == buf->actual_size)
+                                if (ubuf->actual_size == buf->actual_size) {
                                         memcpy(ubuf->data, buf->cpu,
                                                 ubuf->actual_size);
+                                } else {
+                                        printk(KERN_ERR "buf %p actual fails match\n", buf);
+                                }
 
                                 /* Requeue the buffer on the free list */
                                 ubuf->pos = 0;
@@ -297,7 +315,7 @@ static void saa7164_work_enchandler(struct work_struct *w)
                         /* Ensure offset into buffer remains 0, fill buffer
                          * with known bad data. */
                         saa7164_buffer_zero_offsets(port, rp);
-                        memset(buf->cpu, 0xDE, buf->pci_size);
+                        memset(buf->cpu, 0xff, buf->pci_size);
 
                         break;
                 }
diff --git a/drivers/media/video/saa7164/saa7164-encoder.c b/drivers/media/video/saa7164/saa7164-encoder.c
index 5f73ceded31..c61907d0efb 100644
--- a/drivers/media/video/saa7164/saa7164-encoder.c
+++ b/drivers/media/video/saa7164/saa7164-encoder.c
@@ -1038,14 +1038,18 @@ static ssize_t fops_read(struct file *file, char __user *buffer,
         saa7164_histogram_update(&port->read_interval,
                 port->last_read_msecs_diff);
 
-        if (*pos)
+        if (*pos) {
+                printk(KERN_ERR "%s() ESPIPE\n", __func__);
                 return -ESPIPE;
+        }
 
         if (atomic_cmpxchg(&fh->v4l_reading, 0, 1) == 0) {
                 if (atomic_inc_return(&port->v4l_reader_count) == 1) {
 
-                        if (saa7164_encoder_initialize(port) < 0)
+                        if (saa7164_encoder_initialize(port) < 0) {
+                                printk(KERN_ERR "%s() EINVAL\n", __func__);
                                 return -EINVAL;
+                        }
 
                         saa7164_encoder_start_streaming(port);
                         msleep(200);
@@ -1056,6 +1060,7 @@ static ssize_t fops_read(struct file *file, char __user *buffer,
         if ((file->f_flags & O_NONBLOCK) == 0) {
                 if (wait_event_interruptible(port->wait_read,
                         saa7164_enc_next_buf(port))) {
+                                printk(KERN_ERR "%s() ERESTARTSYS\n", __func__);
                                 return -ERESTARTSYS;
                 }
         }
@@ -1077,8 +1082,10 @@ static ssize_t fops_read(struct file *file, char __user *buffer,
 
                 if (copy_to_user(buffer, p, cnt)) {
                         printk(KERN_ERR "%s() copy_to_user failed\n", __func__);
-                        if (!ret)
+                        if (!ret) {
+                                printk(KERN_ERR "%s() EFAULT\n", __func__);
                                 ret = -EFAULT;
+                        }
                         goto err;
                 }
 
@@ -1087,6 +1094,10 @@ static ssize_t fops_read(struct file *file, char __user *buffer,
                 buffer += cnt;
                 ret += cnt;
 
+                if (ubuf->pos > ubuf->actual_size) {
+                        printk(KERN_ERR "read() pos > actual, huh?\n");
+                }
+
                 if (ubuf->pos == ubuf->actual_size) {
 
                         /* finished with current buffer, take next buffer */
@@ -1109,8 +1120,10 @@ static ssize_t fops_read(struct file *file, char __user *buffer,
                 }
         }
 err:
-        if (!ret && !ubuf)
+        if (!ret && !ubuf) {
+                printk(KERN_ERR "%s() EAGAIN\n", __func__);
                 ret = -EAGAIN;
+        }
 
         return ret;
 }