linux-kernel - [PATCH 3.16 114/366] hugetlbfs: fix bug in pgoff overflow checking

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Message-ID: <lsq.1539530741.559926046@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Michal Hocko" <mhocko@...nel.org>,
        "Nic Losby" <blurbdust@...il.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Dan Rue" <dan.rue@...aro.org>,
        "Yisheng Xie" <xieyisheng1@...wei.com>,
        "Anders Roxell" <anders.roxell@...aro.org>,
        "Mike Kravetz" <mike.kravetz@...cle.com>
Subject: [PATCH 3.16 114/366] hugetlbfs: fix bug in pgoff overflow checking

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mike Kravetz <mike.kravetz@...cle.com>

commit 5df63c2a149ae65a9ec239e7c2af44efa6f79beb upstream.

This is a fix for a regression in 32 bit kernels caused by an invalid
check for pgoff overflow in hugetlbfs mmap setup.  The check incorrectly
specified that the size of a loff_t was the same as the size of a long.
The regression prevents mapping hugetlbfs files at offsets greater than
4GB on 32 bit kernels.

On 32 bit kernels conversion from a page based unsigned long can not
overflow a loff_t byte offset.  Therefore, skip this check if
sizeof(unsigned long) != sizeof(loff_t).

Link: http://lkml.kernel.org/r/20180330145402.5053-1-mike.kravetz@oracle.com
Fixes: 63489f8e8211 ("hugetlbfs: check for pgoff value overflow")
Reported-by: Dan Rue <dan.rue@...aro.org>
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
Tested-by: Anders Roxell <anders.roxell@...aro.org>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Yisheng Xie <xieyisheng1@...wei.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Nic Losby <blurbdust@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/hugetlbfs/inode.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -127,10 +127,14 @@ static int hugetlbfs_file_mmap(struct fi
 
 	/*
 	 * page based offset in vm_pgoff could be sufficiently large to
-	 * overflow a (l)off_t when converted to byte offset.
+	 * overflow a loff_t when converted to byte offset.  This can
+	 * only happen on architectures where sizeof(loff_t) ==
+	 * sizeof(unsigned long).  So, only check in those instances.
 	 */
-	if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
-		return -EINVAL;
+	if (sizeof(unsigned long) == sizeof(loff_t)) {
+		if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
+			return -EINVAL;
+	}
 
 	/* must be huge page aligned */
 	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))