[PATCH 3.12 042/119] s390/sclp_ctl: fix potential information leak with /dev/sclp
From: Jiri Slaby <hidden>
Date: 2016-09-29 10:48:07
Also in:
lkml
Subsystem:
s390 architecture, the rest · Maintainers:
Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Linus Torvalds
From: Martin Schwidefsky <redacted> 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 <redacted> Reviewed-by: Michael Holzheu <redacted> Signed-off-by: Martin Schwidefsky <redacted> Signed-off-by: Juerg Haefliger <redacted> Signed-off-by: Jiri Slaby <redacted> --- drivers/s390/char/sclp_ctl.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/s390/char/sclp_ctl.c b/drivers/s390/char/sclp_ctl.c
index 648cb86afd42..ea607a4a1bdd 100644
--- 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 __user *user_area) { 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 __user *user_area) 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);
--
2.10.0