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| author | Meng Xu <mengxu.gatech@gmail.com> | 2017-09-19 07:21:56 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2017-09-19 22:03:59 +0200 |
| commit | e1af344df4e5c8fe90f4a63235a68d5405afc41b (patch) | |
| tree | b230497f54de3a989062c5cb983ef1bed9507074 /sound/pci/asihpi | |
| parent | ALSA: compress: Remove unused variable (diff) | |
| download | linux-e1af344df4e5c8fe90f4a63235a68d5405afc41b.tar.xz linux-e1af344df4e5c8fe90f4a63235a68d5405afc41b.zip | |
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/pci/asihpi')
| -rw-r--r-- | sound/pci/asihpi/hpioctl.c | 12 |
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; |