[Qemu-devel] [PATCH RFC 21/36] 9pfs: local: truncate: don't follow symlinks

[Greg Kurz]

This fixes CVE-2016-9602 for all security models.

Signed-off-by: Greg Kurz <address@hidden>
---
 hw/9pfs/9p-local.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 1f9239de07e5..4377aa6524c2 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -1231,15 +1231,16 @@ out:
     return ret;
 }
 
-static int local_truncate(FsContext *ctx, V9fsPath *fs_path, off_t size)
+static int local_truncate(FsContext *fs_ctx, V9fsPath *fs_path, off_t size)
 {
-    char *buffer;
-    int ret;
-    char *path = fs_path->data;
+    int fd, ret;
 
-    buffer = rpath(ctx, path);
-    ret = truncate(buffer, size);
-    g_free(buffer);
+    fd = local_open_nofollow(fs_ctx, fs_path->data, O_WRONLY, 0);
+    if (fd == -1) {
+        return -1;
+    }
+    ret = ftruncate(fd, size);
+    close_preserve_errno(fd);
     return ret;
 }