From ba42ebb863ab7d40adc79298422ed9596df8f73a Mon Sep 17 00:00:00 2001 From: Li Qiang Date: Mon, 17 Oct 2016 14:13:58 +0200 Subject: [PATCH] 9pfs: allocate space for guest originated empty strings If a guest sends an empty string paramater to any 9P operation, the current code unmarshals it into a V9fsString equal to { .size = 0, .data = NULL }. This is unfortunate because it can cause NULL pointer dereference to happen at various locations in the 9pfs code. And we don't want to check str->data everywhere we pass it to strcmp() or any other function which expects a dereferenceable pointer. This patch enforces the allocation of genuine C empty strings instead, so callers don't have to bother. Out of all v9fs_iov_vunmarshal() users, only v9fs_xattrwalk() checks if the returned string is empty. It now uses v9fs_string_size() since name.data cannot be NULL anymore. Signed-off-by: Li Qiang [groug, rewritten title and changelog, fix empty string check in v9fs_xattrwalk()] Signed-off-by: Greg Kurz --- fsdev/9p-iov-marshal.c | 2 +- hw/9pfs/9p.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c index 663cad5..1d16f8d 100644 --- a/fsdev/9p-iov-marshal.c +++ b/fsdev/9p-iov-marshal.c @@ -125,7 +125,7 @@ ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset, str->data = g_malloc(str->size + 1); copied = v9fs_unpack(str->data, out_sg, out_num, offset, str->size); - if (copied > 0) { + if (copied >= 0) { str->data[str->size] = 0; } else { v9fs_string_free(str); diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 119ee58..39a7e1d 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -3174,7 +3174,7 @@ static void v9fs_xattrwalk(void *opaque) goto out; } v9fs_path_copy(&xattr_fidp->path, &file_fidp->path); - if (name.data == NULL) { + if (!v9fs_string_size(&name)) { /* * listxattr request. Get the size first */ -- 2.7.3