Patch "tcm_fileio: Prevent information leak for short reads" has been added to the 4.4-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tcm_fileio: Prevent information leak for short reads

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcm_fileio-prevent-information-leak-for-short-reads.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From foo@baz Thu Mar 22 14:57:32 CET 2018
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Date: Fri, 31 Mar 2017 19:53:35 +0400
Subject: tcm_fileio: Prevent information leak for short reads

From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>


[ Upstream commit f11b55d13563e9428c88c873f4f03a6bef11ec0a ]

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.

(Change BUG_ON into -EINVAL se_cmd failure - nab)

testcase: https://github.com/dmonakhov/xfstests/commit/e11a1b7b907ca67b1be51a1594025600767366d5
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/target/target_core_file.c |   23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -276,12 +276,11 @@ static int fd_do_rw(struct se_cmd *cmd,
 	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 {
 		/*
@@ -294,17 +293,29 @@ static int fd_do_rw(struct se_cmd *cmd,
 				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.
+				 */
+				if (ret < data_length)
+					ret += iov_iter_zero(data_length - ret, &iter);
+				else
+					ret = -EINVAL;
 			}
 		}
 	}
-	return 1;
+	kfree(bvec);
+	return ret;
 }
 
 static sense_reason_t


Patches currently in stable-queue which might be from dmonakhov@xxxxxxxxxx are

queue-4.4/tcm_fileio-prevent-information-leak-for-short-reads.patch