linux-kernel - [PATCH] drivers: char: mem: Check for address space wraparound with mmap()

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20170512214258.10860-1-jwerner@chromium.org>
Date:   Fri, 12 May 2017 14:42:58 -0700
From:   Julius Werner <jwerner@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Aaron Durbin <adurbin@...omium.org>,
        Julius Werner <jwerner@...omium.org>
Subject: [PATCH] drivers: char: mem: Check for address space wraparound with mmap()

/dev/mem currently allows mmap() mappings that wrap around the end of
the physical address space, which should probably be illegal. It
circumvents the existing STRICT_DEVMEM permission check because the loop
immediately terminates (as the start address is already higher than the
end address). On the x86_64 architecture it will then cause a panic
(from the BUG(start >= end) in arch/x86/mm/pat.c:reserve_memtype()).

This patch adds an explicit check to make sure offset + size will not
wrap around in the physical address type.

Signed-off-by: Julius Werner <jwerner@...omium.org>
---
 drivers/char/mem.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 7e4a9d1296bb..6e0cbe092220 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -340,6 +340,11 @@ static const struct vm_operations_struct mmap_mem_ops = {
 static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 {
 	size_t size = vma->vm_end - vma->vm_start;
+	phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
+
+	/* It's illegal to wrap around the end of the physical address space. */
+	if (offset + (phys_addr_t)size < offset)
+		return -EINVAL;

 	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 		return -EINVAL;
-- 
2.12.2