linux-kernel - [34-longterm 195/196] befs: Validate length of long symbolic links.

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Date:	Mon, 12 Mar 2012 20:21:48 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Timo Warns <Warns@...-sense.de>,
	Timo Warns <warns@...-sense.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 195/196] befs: Validate length of long symbolic links.

From: Timo Warns <Warns@...-sense.de>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 338d0f0a6fbc82407864606f5b64b75aeb3c70f2 upstream.

Signed-off-by: Timo Warns <warns@...-sense.de>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 fs/befs/linuxvfs.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index 34ddda8..9158c07 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -469,17 +469,22 @@ befs_follow_link(struct dentry *dentry, struct nameidata *nd)
 		befs_data_stream *data = &befs_ino->i_data.ds;
 		befs_off_t len = data->size;
 
-		befs_debug(sb, "Follow long symlink");
-
-		link = kmalloc(len, GFP_NOFS);
-		if (!link) {
-			link = ERR_PTR(-ENOMEM);
-		} else if (befs_read_lsymlink(sb, data, link, len) != len) {
-			kfree(link);
-			befs_error(sb, "Failed to read entire long symlink");
+		if (len == 0) {
+			befs_error(sb, "Long symlink with illegal length");
 			link = ERR_PTR(-EIO);
 		} else {
-			link[len - 1] = '\0';
+			befs_debug(sb, "Follow long symlink");
+
+			link = kmalloc(len, GFP_NOFS);
+			if (!link) {
+				link = ERR_PTR(-ENOMEM);
+			} else if (befs_read_lsymlink(sb, data, link, len) != len) {
+				kfree(link);
+				befs_error(sb, "Failed to read entire long symlink");
+				link = ERR_PTR(-EIO);
+			} else {
+				link[len - 1] = '\0';
+			}
 		}
 	} else {
 		link = befs_ino->i_data.symlink;
-- 
1.7.9.3

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