File 0297-9pfs-fix-integer-overflow-issue-in-.patch of Package qemu.3557

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File 0297-9pfs-fix-integer-overflow-issue-in-.patch of Package qemu.3557

From 3ce6188cd428913ccb0b285d9d9fdac7e16932b9 Mon Sep 17 00:00:00 2001
From: Li Qiang <liqiang6-s@360.cn>
Date: Tue, 1 Nov 2016 12:00:40 +0100
Subject: [PATCH] 9pfs: fix integer overflow issue in xattr read/write
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The v9fs_xattr_read() and v9fs_xattr_write() are passed a guest
originated offset: they must ensure this offset does not go beyond
the size of the extended attribute that was set in v9fs_xattrcreate().
Unfortunately, the current code implement these checks with unsafe
calculations on 32 and 64 bit values, which may allow a malicious
guest to cause OOB access anyway.

Fix this by comparing the offset and the xattr size, which are
both uint64_t, before trying to compute the effective number of bytes
to read or write.

Suggested-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Li Qiang <liqiang6-s@360.cn>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-By: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 7e55d65c56a03dcd2c5d7c49d37c5a74b55d4bd6)
[BR: CVE-2016-9104 BSC#1007493]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 hw/9pfs/virtio-9p.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index 2c30422..10172e0 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -1580,18 +1580,15 @@ static int v9fs_xattr_read(V9fsState *s, V9fsPDU *pdu, V9fsFidState *fidp,
 {
     ssize_t err;
     size_t offset = 7;
-    int read_count;
-    int64_t xattr_len;
+    uint64_t read_count;
 
-    xattr_len = fidp->fs.xattr.len;
-    read_count = xattr_len - off;
+    if (fidp->fs.xattr.len < off) {
+        read_count = 0;
+    } else {
+        read_count = fidp->fs.xattr.len - off;
+    }
     if (read_count > max_count) {
         read_count = max_count;
-    } else if (read_count < 0) {
-        /*
-         * read beyond XATTR value
-         */
-        read_count = 0;
     }
     err = pdu_marshal(pdu, offset, "d", read_count);
     if (err < 0) {
@@ -1916,23 +1913,18 @@ static int v9fs_xattr_write(V9fsState *s, V9fsPDU *pdu, V9fsFidState *fidp,
 {
     int i, to_copy;
     ssize_t err = 0;
-    int write_count;
-    int64_t xattr_len;
+    uint64_t write_count;
     size_t offset = 7;
 
 
-    xattr_len = fidp->fs.xattr.len;
-    write_count = xattr_len - off;
-    if (write_count > count) {
-        write_count = count;
-    } else if (write_count < 0) {
-        /*
-         * write beyond XATTR value len specified in
-         * xattrcreate
-         */
+    if (fidp->fs.xattr.len < off) {
         err = -ENOSPC;
         goto out;
     }
+    write_count = fidp->fs.xattr.len - off;
+    if (write_count > count) {
+        write_count = count;
+    }
     err = pdu_marshal(pdu, offset, "d", write_count);
     if (err < 0) {
         return err;

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