File 0461-9p-take-write-lock-on-fid-path-upda.patch of Package qemu.11147

From b6ae861bb81c36e39f43017221e7631197eb5249 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Tue, 20 Nov 2018 13:00:35 +0100
Subject: [PATCH] 9p: take write lock on fid path updates (CVE-2018-19364)

Recent commit 5b76ef50f62079a fixed a race where v9fs_co_open2() could
possibly overwrite a fid path with v9fs_path_copy() while it is being
accessed by some other thread, ie, use-after-free that can be detected
by ASAN with a custom 9p client.

It turns out that the same can happen at several locations where
v9fs_path_copy() is used to set the fid path. The fix is again to
take the write lock.

Fixes CVE-2018-19364.

Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 5b3c77aa581ebb215125c84b0742119483571e55)
[BR: BSC#1116717 CVE-2018-19364]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 hw/9pfs/9p.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 7f68c180b3..d7d3e1dae2 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1341,7 +1341,9 @@ static void v9fs_walk(void *opaque)
     }
     if (fid == newfid) {
         BUG_ON(fidp->fid_type != P9_FID_NONE);
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
     } else {
         newfidp = alloc_fid(s, newfid);
         if (newfidp == NULL) {
@@ -2073,6 +2075,7 @@ static void v9fs_create(void *opaque)
     V9fsString extension;
     int iounit;
     V9fsPDU *pdu = opaque;
+    V9fsState *s = pdu->s;
 
     v9fs_path_init(&path);
     v9fs_string_init(&name);
@@ -2103,7 +2106,9 @@ static void v9fs_create(void *opaque)
         if (err < 0) {
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
         err = v9fs_co_opendir(pdu, fidp);
         if (err < 0) {
             goto out;
@@ -2119,7 +2124,9 @@ static void v9fs_create(void *opaque)
         if (err < 0) {
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
     } else if (perm & P9_STAT_MODE_LINK) {
         int32_t ofid = atoi(extension.data);
         V9fsFidState *ofidp = get_fid(pdu, ofid);
@@ -2137,7 +2144,9 @@ static void v9fs_create(void *opaque)
             fidp->fid_type = P9_FID_NONE;
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
         err = v9fs_co_lstat(pdu, &fidp->path, &stbuf);
         if (err < 0) {
             fidp->fid_type = P9_FID_NONE;
@@ -2175,7 +2184,9 @@ static void v9fs_create(void *opaque)
         if (err < 0) {
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
     } else if (perm & P9_STAT_MODE_NAMED_PIPE) {
         err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,
                             0, S_IFIFO | (perm & 0777), &stbuf);
@@ -2186,7 +2197,9 @@ static void v9fs_create(void *opaque)
         if (err < 0) {
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
     } else if (perm & P9_STAT_MODE_SOCKET) {
         err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,
                             0, S_IFSOCK | (perm & 0777), &stbuf);
@@ -2197,7 +2210,9 @@ static void v9fs_create(void *opaque)
         if (err < 0) {
             goto out;
         }
+        v9fs_path_write_lock(s);
         v9fs_path_copy(&fidp->path, &path);
+        v9fs_path_unlock(s);
     } else {
         err = v9fs_co_open2(pdu, fidp, &name, -1,
                             omode_to_uflags(mode)|O_CREAT, perm, &stbuf);