Patch "staging: lustre: hsm: stack overrun in hai_dump_data_field" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    staging: lustre: hsm: stack overrun in hai_dump_data_field

to the 4.9-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:
     staging-lustre-hsm-stack-overrun-in-hai_dump_data_field.patch
and it can be found in the queue-4.9 subdirectory.

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


>From foo@baz Mon Nov  6 10:07:35 CET 2017
From: frank zago <fzago@cray.com>
Date: Sat, 7 Oct 2017 22:36:54 +0000
Subject: staging: lustre: hsm: stack overrun in hai_dump_data_field

From: frank zago <fzago@cray.com>


[ Upstream commit 22aadb91c0a0055935109c175f5446abfb130702 ]

The function hai_dump_data_field will do a stack buffer
overrun when cat'ing /sys/fs/lustre/.../hsm/actions if an action has
some data in it.

hai_dump_data_field uses snprintf. But there is no check for
truncation, and the value returned by snprintf is used as-is.  The
coordinator code calls hai_dump_data_field with 12 bytes in the
buffer. The 6th byte of data is printed incompletely to make room for
the terminating NUL. However snprintf still returns 2, so when
hai_dump_data_field writes the final NUL, it does it outside the
reserved buffer, in the 13th byte of the buffer. This stack buffer
overrun hangs my VM.

Fix by checking that there is enough room for the next 2 characters
plus the NUL terminator. Don't print half bytes. Change the format to
02X instead of .2X, which makes more sense.

Signed-off-by: frank zago <fzago@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8171
Reviewed-on: http://review.whamcloud.com/20338
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Jean-Baptiste Riaux <riaux.jb@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/lustre/lustre/include/lustre/lustre_user.h |   18 +++++--------
 1 file changed, 8 insertions(+), 10 deletions(-)

--- a/drivers/staging/lustre/lustre/include/lustre/lustre_user.h
+++ b/drivers/staging/lustre/lustre/include/lustre/lustre_user.h
@@ -1213,23 +1213,21 @@ struct hsm_action_item {
  * \retval buffer
  */
 static inline char *hai_dump_data_field(struct hsm_action_item *hai,
-					char *buffer, int len)
+					char *buffer, size_t len)
 {
-	int i, sz, data_len;
+	int i, data_len;
 	char *ptr;
 
 	ptr = buffer;
-	sz = len;
 	data_len = hai->hai_len - sizeof(*hai);
-	for (i = 0 ; (i < data_len) && (sz > 0) ; i++) {
-		int cnt;
-
-		cnt = snprintf(ptr, sz, "%.2X",
-			       (unsigned char)hai->hai_data[i]);
-		ptr += cnt;
-		sz -= cnt;
+	for (i = 0; (i < data_len) && (len > 2); i++) {
+		snprintf(ptr, 3, "%02X", (unsigned char)hai->hai_data[i]);
+		ptr += 2;
+		len -= 2;
 	}
+
 	*ptr = '\0';
+
 	return buffer;
 }
 


Patches currently in stable-queue which might be from fzago@cray.com are

queue-4.9/staging-lustre-hsm-stack-overrun-in-hai_dump_data_field.patch