linux-kernel - [PATCH 41/48] staging/lustre/llite: error of listxattr when buffer is small

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Date:	Tue, 23 Jul 2013 00:07:02 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Keith Mannthey <keith.mannthey@...el.com>,
	Peng Tao <tao.peng@....com>,
	Andreas Dilger <andreas.dilger@...el.com>
Subject: [PATCH 41/48] staging/lustre/llite: error of listxattr when buffer is small

From: Keith Mannthey <keith.mannthey@...el.com>

According to the standard, listxattr(2) should return -1
and errno should be set to ERANGE if the size of the list
buffer is too small to hold the result. However ll_listxattr()
will return a value bigger than the size of buffer in some cases.

Let's assume listxattr(2) returns SIZE when it is called with a
large enough list buffer. If it's called again with a list buffer
whose size is smaller than SIZE but bigger than (SIZE - 12), then
listxattr(2) will return SIZE too. This patch fixes the problem.
Original patch by Li Xi <pkuelelixi@...il.com>

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3403
Lustre-change: http://review.whamcloud.com/6463
Signed-off-by: Keith Mannthey <keith.mannthey@...el.com>
Reviewed-by: Li Xi <pkuelelixi@...il.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@...el.com>
Reviewed-by: Oleg Drokin <oleg.drokin@...el.com>
Signed-off-by: Peng Tao <tao.peng@....com>
Signed-off-by: Andreas Dilger <andreas.dilger@...el.com>
---
 drivers/staging/lustre/lustre/llite/xattr.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lustre/llite/xattr.c b/drivers/staging/lustre/lustre/llite/xattr.c
index 0a11902..2e3ff6d 100644
--- a/drivers/staging/lustre/lustre/llite/xattr.c
+++ b/drivers/staging/lustre/lustre/llite/xattr.c
@@ -564,7 +564,12 @@ ssize_t ll_listxattr(struct dentry *dentry, char *buffer, size_t size)
 		const size_t name_len   = sizeof("lov") - 1;
 		const size_t total_len  = prefix_len + name_len + 1;
 
-		if (buffer && (rc + total_len) <= size) {
+		if (((rc + total_len) > size) && (buffer != NULL)) {
+			ptlrpc_req_finished(request);
+			return -ERANGE;
+		}
+
+		if (buffer != NULL) {
 			buffer += rc;
 			memcpy(buffer, XATTR_LUSTRE_PREFIX, prefix_len);
 			memcpy(buffer + prefix_len, "lov", name_len);
-- 
1.7.9.5

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