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Commit e1af344d authored by Meng Xu's avatar Meng Xu Committed by Takashi Iwai
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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: default avatarMeng Xu <mengxu.gatech@gmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a931b9ce

sound/pci/asihpi/hpioctl.c

+8 −4
Original line number Diff line number Diff line
@@ -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;