3.16.37-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
commit 532c34b5fbf1687df63b3fcd5b2846312ac943c6 upstream.
The sclp_ctl_ioctl_sccb function uses two copy_from_user calls to
retrieve the sclp request from user space. The first copy_from_user
fetches the length of the request which is stored in the first two
bytes of the request. The second copy_from_user gets the complete
sclp request, but this copies the length field a second time.
A malicious user may have changed the length in the meantime.
Reported-by: Pengfei Wang <wpengfeinudt@xxxxxxxxx>
Reviewed-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
drivers/s390/char/sclp_ctl.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/drivers/s390/char/sclp_ctl.c
+++ b/drivers/s390/char/sclp_ctl.c
@@ -56,6 +56,7 @@ static int sclp_ctl_ioctl_sccb(void __us
{
struct sclp_ctl_sccb ctl_sccb;
struct sccb_header *sccb;
+ unsigned long copied;
int rc;
if (copy_from_user(&ctl_sccb, user_area, sizeof(ctl_sccb)))
@@ -65,14 +66,15 @@ static int sclp_ctl_ioctl_sccb(void __us
sccb = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
if (!sccb)
return -ENOMEM;
- if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sizeof(*sccb))) {
+ copied = PAGE_SIZE -
+ copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), PAGE_SIZE);
+ if (offsetof(struct sccb_header, length) +
+ sizeof(sccb->length) > copied || sccb->length > copied) {
rc = -EFAULT;
goto out_free;
}
- if (sccb->length > PAGE_SIZE || sccb->length < 8)
- return -EINVAL;
- if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sccb->length)) {
- rc = -EFAULT;
+ if (sccb->length < 8) {
+ rc = -EINVAL;
goto out_free;
}
rc = sclp_sync_request(ctl_sccb.cmdw, sccb);
--
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