linux-kernel - [PATCH] Revert "mm/usercopy: Drop extra is_vmalloc_or

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Date:   Thu, 23 Dec 2021 18:21:26 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        "Mark Rutland" <mark.rutland@....com>, <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Paul Mackerras" <paulus@...ba.org>,
        <linuxppc-dev@...ts.ozlabs.org>
CC:     Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: [PATCH] Revert "mm/usercopy: Drop extra is_vmalloc_or_module() check"

This reverts commit 517e1fbeb65f5eade8d14f46ac365db6c75aea9b.

  usercopy: Kernel memory exposure attempt detected from SLUB object not in SLUB page?! (offset 0, size 1048)!
  kernel BUG at mm/usercopy.c:99
  ...
  usercopy_abort+0x64/0xa0 (unreliable)
  __check_heap_object+0x168/0x190
  __check_object_size+0x1a0/0x200
  dev_ethtool+0x2494/0x2b20
  dev_ioctl+0x5d0/0x770
  sock_do_ioctl+0xf0/0x1d0
  sock_ioctl+0x3ec/0x5a0
  __se_sys_ioctl+0xf0/0x160
  system_call_exception+0xfc/0x1f0
  system_call_common+0xf8/0x200

When run ethtool eth0, the BUG occurred, the code shows below,

  data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
  copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))

The data is alloced by vmalloc(),  virt_addr_valid(ptr) will return true
on PowerPC64, which leads to the panic, add back the is_vmalloc_or_module()
check to fix it.

Fixes: 517e1fbeb65f (mm/usercopy: Drop extra is_vmalloc_or_module() check)
Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
---
 mm/usercopy.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/usercopy.c b/mm/usercopy.c
index b3de3c4eefba..cfc845403017 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -225,6 +225,17 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 {
 	struct page *page;

+	/*
+	 * Some architectures (PowerPC64) return true for virt_addr_valid() on
+	 * vmalloced addresses. Work around this by checking for vmalloc
+	 * first.
+	 *
+	 * We also need to check for module addresses explicitly since we
+	 * may copy static data from modules to userspace
+	 */
+	if (is_vmalloc_or_module_addr(ptr))
+		return;
+
 	if (!virt_addr_valid(ptr))
 		return;

-- 
2.26.2