path: root/sound
diff options
authorMeng Xu <mengxu.gatech@gmail.com>2017-09-19 01:21:56 -0400
committerTakashi Iwai <tiwai@suse.de>2017-09-19 22:03:59 +0200
commite1af344df4e5c8fe90f4a63235a68d5405afc41b (patch)
treeb230497f54de3a989062c5cb983ef1bed9507074 /sound
parentALSA: compress: Remove unused variable (diff)
ALSA: asihpi: fix a potential double-fetch bug when copying puhm
The hm->h.size is intended to hold the actual size of the hm struct that is copied from userspace and should always be <= sizeof(*hm). However, after copy_from_user(hm, puhm, hm->h.size), since userspace process has full control over the memory region pointed by puhm, it is possible that the value of hm->h.size is different from what is fetched-in previously (get_user(hm->h.size, (u16 __user *)puhm)). In other words, hm->h.size is overriden and the relation between hm->h.size and the hm struct is broken. This patch proposes to use a seperate variable, msg_size, to hold the value of the first fetch and override hm->h.size to msg_size after the second fetch to maintain the relation. Signed-off-by: Meng Xu <mengxu.gatech@gmail.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
1 files changed, 8 insertions, 4 deletions
diff --git a/sound/pci/asihpi/hpioctl.c b/sound/pci/asihpi/hpioctl.c
index 7e3aa50b21f9..5badd08e1d69 100644
--- a/sound/pci/asihpi/hpioctl.c
+++ b/sound/pci/asihpi/hpioctl.c
@@ -103,6 +103,7 @@ long asihpi_hpi_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
void __user *puhr;
union hpi_message_buffer_v1 *hm;
union hpi_response_buffer_v1 *hr;
+ u16 msg_size;
u16 res_max_size;
u32 uncopied_bytes;
int err = 0;
@@ -127,22 +128,25 @@ long asihpi_hpi_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
/* Now read the message size and data from user space. */
- if (get_user(hm->h.size, (u16 __user *)puhm)) {
+ if (get_user(msg_size, (u16 __user *)puhm)) {
err = -EFAULT;
goto out;
- if (hm->h.size > sizeof(*hm))
- hm->h.size = sizeof(*hm);
+ if (msg_size > sizeof(*hm))
+ msg_size = sizeof(*hm);
/* printk(KERN_INFO "message size %d\n", hm->h.wSize); */
- uncopied_bytes = copy_from_user(hm, puhm, hm->h.size);
+ uncopied_bytes = copy_from_user(hm, puhm, msg_size);
if (uncopied_bytes) {
HPI_DEBUG_LOG(ERROR, "uncopied bytes %d\n", uncopied_bytes);
err = -EFAULT;
goto out;
+ /* Override h.size in case it is changed between two userspace fetches */
+ hm->h.size = msg_size;
if (get_user(res_max_size, (u16 __user *)puhr)) {
err = -EFAULT;
goto out;