[1/2] tcm_fileio: Prevent information leak for short reads
diff mbox

Message ID 1490975616-27057-1-git-send-email-dmonakhov@openvz.org
State New, archived
Headers show

Commit Message

Dmitry Monakhov March 31, 2017, 3:53 p.m. UTC
If we failed to read data from backing file (probably because some one
truncate file under us), we must zerofill cmd's data, otherwise it will
be returned as is. Most likely cmd's data are unitialized pages from
page cache. This result in information leak.

testcase: https://github.com/dmonakhov/xfstests/commit/e11a1b7b907ca67b1be51a1594025600767366d5
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 drivers/target/target_core_file.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

Patch
diff mbox

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index 87aa376..d69908d 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -277,12 +277,11 @@  static int fd_do_rw(struct se_cmd *cmd, struct file *fd,
 	else
 		ret = vfs_iter_read(fd, &iter, &pos);
 
-	kfree(bvec);
-
 	if (is_write) {
 		if (ret < 0 || ret != data_length) {
 			pr_err("%s() write returned %d\n", __func__, ret);
-			return (ret < 0 ? ret : -EINVAL);
+			if (ret >= 0)
+				ret = -EINVAL;
 		}
 	} else {
 		/*
@@ -295,17 +294,27 @@  static int fd_do_rw(struct se_cmd *cmd, struct file *fd,
 				pr_err("%s() returned %d, expecting %u for "
 						"S_ISBLK\n", __func__, ret,
 						data_length);
-				return (ret < 0 ? ret : -EINVAL);
+				if (ret >= 0)
+					ret = -EINVAL;
 			}
 		} else {
 			if (ret < 0) {
 				pr_err("%s() returned %d for non S_ISBLK\n",
 						__func__, ret);
-				return ret;
+			} else if (ret != data_length) {
+				/*
+				 * Short read case:
+				 * Probably some one truncate file under us.
+				 * We must explicitly zero sg-pages to prevent
+				 * expose uninizialized pages to userspace.
+				 */
+				BUG_ON(ret > data_length);
+				ret += iov_iter_zero(data_length - ret, &iter);
 			}
 		}
 	}
-	return 1;
+	kfree(bvec);
+	return ret;
 }
 
 static sense_reason_t