[34-longterm 103/209] HID: hidraw, fix a NULL pointer dereference in hidraw_write

From: Paul Gortmaker
Date: Thu Apr 14 2011 - 13:48:40 EST

From: Antonio Ospite <ospite@xxxxxxxxxxxxxxxxx>

| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|

commit e42dee9a99a3ecd32b5c027e8f7411fb5bc11eb6 upstream.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: [<ffffffffa0f0a625>] hidraw_write+0x3b/0x116 [hid]

This is reproducible by disconnecting the device while userspace writes
to dev node in a loop and doesn't check return values in order to exit
the loop.

[PG: slightly/trivially reworked for backport to 34]

Signed-off-by: Antonio Ospite <ospite@xxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
drivers/hid/hidraw.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 0db1a0f..9d3c663 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -106,11 +106,15 @@ out:
static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
unsigned int minor = iminor(file->f_path.dentry->d_inode);
- /* FIXME: What stops hidraw_table going NULL */
- struct hid_device *dev = hidraw_table[minor]->hid;
+ struct hid_device *dev;
__u8 *buf;
int ret = 0;

+ if (!hidraw_table[minor])
+ return -ENODEV;
+ dev = hidraw_table[minor]->hid;
if (!dev->hid_output_raw_report)
return -ENODEV;


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