linux-kernel - [patch] vfs: check for integer overflows in posix_acl

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Message-ID: <20130624162719.GB32503@elgon.mountain>
Date:	Mon, 24 Jun 2013 19:27:19 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [patch] vfs: check for integer overflows in posix_acl_alloc()

We've seen cases where people passed negative numbers to
posix_acl_alloc() and we fixed the caller.  For example 093019cf1b "xfs:
fix acl count validation in xfs_acl_from_disk()".  But there are other
places which might be affected like ext4_acl_from_disk() which checks
for negative but doesn't check an upper limit.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index cea4623..cd7fd2f 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -46,7 +46,12 @@ posix_acl_alloc(int count, gfp_t flags)
 {
 	const size_t size = sizeof(struct posix_acl) +
 	                    count * sizeof(struct posix_acl_entry);
-	struct posix_acl *acl = kmalloc(size, flags);
+	struct posix_acl *acl;
+
+	if (count < 0 || count > (SIZE_MAX - sizeof(struct posix_acl) /
+					sizeof(struct posix_acl_entry)))
+		return NULL;
+	acl = kmalloc(size, flags);
 	if (acl)
 		posix_acl_init(acl, count);
 	return acl;
--
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