qemu: Security fix for CVE-2018-19489

Source: Qemu.org
MR: 97453
Type: Security Fix
Disposition: Backport from git.qemu.org/gemu.git

ChangeID: a06fcb432d447cec2ed1caf112822dd1b4831ace
Description:

In the spirt of YP Compatible, sending change upstream.

fixes CVE CVE-2018-19489

Affect < = 4.0.0

(From OE-Core rev: 249447828cd1ed13f9faf19793208b503acf0d30)

Signed-off-by: Armin Kuster <akuster@mvista.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemu/CVE-2018-19489.patch

@@ -0,0 +1,83 @@
+From 1d20398694a3b67a388d955b7a945ba4aa90a8a8 Mon Sep 17 00:00:00 2001
+From: Greg Kurz <groug@kaod.org>
+Date: Fri, 23 Nov 2018 13:28:03 +0100
+Subject: [PATCH] 9p: fix QEMU crash when renaming files
+
+When using the 9P2000.u version of the protocol, the following shell
+command line in the guest can cause QEMU to crash:
+
+    while true; do rm -rf aa; mkdir -p a/b & touch a/b/c & mv a aa; done
+
+With 9P2000.u, file renaming is handled by the WSTAT command. The
+v9fs_wstat() function calls v9fs_complete_rename(), which calls
+v9fs_fix_path() for every fid whose path is affected by the change.
+The involved calls to v9fs_path_copy() may race with any other access
+to the fid path performed by some worker thread, causing a crash like
+shown below:
+
+Thread 12 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
+0x0000555555a25da2 in local_open_nofollow (fs_ctx=0x555557d958b8, path=0x0,
+ flags=65536, mode=0) at hw/9pfs/9p-local.c:59
+59          while (*path && fd != -1) {
+(gdb) bt
+#0  0x0000555555a25da2 in local_open_nofollow (fs_ctx=0x555557d958b8,
+ path=0x0, flags=65536, mode=0) at hw/9pfs/9p-local.c:59
+#1  0x0000555555a25e0c in local_opendir_nofollow (fs_ctx=0x555557d958b8,
+ path=0x0) at hw/9pfs/9p-local.c:92
+#2  0x0000555555a261b8 in local_lstat (fs_ctx=0x555557d958b8,
+ fs_path=0x555556b56858, stbuf=0x7fff84830ef0) at hw/9pfs/9p-local.c:185
+#3  0x0000555555a2b367 in v9fs_co_lstat (pdu=0x555557d97498,
+ path=0x555556b56858, stbuf=0x7fff84830ef0) at hw/9pfs/cofile.c:53
+#4  0x0000555555a1e9e2 in v9fs_stat (opaque=0x555557d97498)
+ at hw/9pfs/9p.c:1083
+#5  0x0000555555e060a2 in coroutine_trampoline (i0=-669165424, i1=32767)
+ at util/coroutine-ucontext.c:116
+#6  0x00007fffef4f5600 in __start_context () at /lib64/libc.so.6
+#7  0x0000000000000000 in  ()
+(gdb)
+
+The fix is to take the path write lock when calling v9fs_complete_rename(),
+like in v9fs_rename().
+
+Impact:  DoS triggered by unprivileged guest users.
+
+Fixes: CVE-2018-19489
+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>
+
+Upstream-Status: Backport
+Affects: < 4.0.0
+CVE: CVE-2018-19489
+Signed-off-by: Armin Kuster <akuster@mvista.com>
+
+---
+ hw/9pfs/9p.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
+index 267a255..bdf7919 100644
+--- a/hw/9pfs/9p.c
++++ b/hw/9pfs/9p.c
+@@ -2855,6 +2855,7 @@ static void coroutine_fn v9fs_wstat(void *opaque)
+     struct stat stbuf;
+     V9fsFidState *fidp;
+     V9fsPDU *pdu = opaque;
++    V9fsState *s = pdu->s;
+ 
+     v9fs_stat_init(&v9stat);
+     err = pdu_unmarshal(pdu, offset, "dwS", &fid, &unused, &v9stat);
+@@ -2920,7 +2921,9 @@ static void coroutine_fn v9fs_wstat(void *opaque)
+         }
+     }
+     if (v9stat.name.size != 0) {
++        v9fs_path_write_lock(s);
+         err = v9fs_complete_rename(pdu, fidp, -1, &v9stat.name);
++        v9fs_path_unlock(s);
+         if (err < 0) {
+             goto out;
+         }
+-- 
+2.7.4
+

meta/recipes-devtools/qemu/qemu_3.0.0.bb

@@ -30,6 +30,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://CVE-2018-18849.patch \
            file://CVE-2018-19364_p1.patch \
            file://CVE-2018-19364_p2.patch \
+           file://CVE-2018-19489.patch \
            "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"