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From 5b3c77aa581ebb215125c84b0742119483571e55 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>
Upstream-status: Backport
Affects: < 3.1.0
CVE: CVE-2018-19364 patch #2
Signed-off-by: Armin Kuster <akuster@mvista.com>
---
hw/9pfs/9p.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index eef289e..267a255 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1391,7 +1391,9 @@ static void coroutine_fn v9fs_walk(void *opaque)
err = -EINVAL;
goto out;
}
+ v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
+ v9fs_path_unlock(s);
} else {
newfidp = alloc_fid(s, newfid);
if (newfidp == NULL) {
@@ -2160,6 +2162,7 @@ static void coroutine_fn v9fs_create(void *opaque)
V9fsString extension;
int iounit;
V9fsPDU *pdu = opaque;
+ V9fsState *s = pdu->s;
v9fs_path_init(&path);
v9fs_string_init(&name);
@@ -2200,7 +2203,9 @@ static void coroutine_fn 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;
@@ -2216,7 +2221,9 @@ static void coroutine_fn 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);
@@ -2234,7 +2241,9 @@ static void coroutine_fn 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;
@@ -2272,7 +2281,9 @@ static void coroutine_fn 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);
@@ -2283,7 +2294,9 @@ static void coroutine_fn 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);
@@ -2294,7 +2307,9 @@ static void coroutine_fn 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);
--
2.7.4
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