From ba42ebb863ab7d40adc79298422ed9596df8f73a Mon Sep 17 00:00:00 2001 From: Li Qiang Date: Mon, 17 Oct 2016 14:13:58 +0200 Subject: 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 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fsdev') diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c index 663cad5429..1d16f8df4b 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); -- cgit v1.2.1