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[Qemu-devel] [PATCH 14/81] 9pfs: local: statfs: don't follow symlinks

From: Michael Roth
Subject: [Qemu-devel] [PATCH 14/81] 9pfs: local: statfs: don't follow symlinks
Date: Mon, 20 Mar 2017 18:07:38 -0500

From: Greg Kurz <address@hidden>

The local_statfs() callback is vulnerable to symlink attacks because it
calls statfs() which follows symbolic links in all path elements.

This patch converts local_statfs() to rely on open_nofollow() and fstatfs()

This partly fixes CVE-2016-9602.

Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
(cherry picked from commit 31e51d1c15b35dc98b88a301812914b70a2b55dc)
Signed-off-by: Greg Kurz <address@hidden>
Signed-off-by: Michael Roth <address@hidden>
 hw/9pfs/9p-local.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index fa1477f..80b3964 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -1078,13 +1078,11 @@ static int local_fsync(FsContext *ctx, int fid_type,
 static int local_statfs(FsContext *s, V9fsPath *fs_path, struct statfs *stbuf)
-    char *buffer;
-    int ret;
-    char *path = fs_path->data;
+    int fd, ret;
-    buffer = rpath(s, path);
-    ret = statfs(buffer, stbuf);
-    g_free(buffer);
+    fd = local_open_nofollow(s, fs_path->data, O_RDONLY, 0);
+    ret = fstatfs(fd, stbuf);
+    close_preserve_errno(fd);
     return ret;

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