diff --git a/include/block/nbd.h b/include/block/nbd.h index 316fd705a9..c306423dc8 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -226,11 +226,11 @@ enum { /* Maximum size of a single READ/WRITE data buffer */ #define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024) -/* Maximum size of an export name. The NBD spec requires 256 and - * suggests that servers support up to 4096, but we stick to only the - * required size so that we can stack-allocate the names, and because - * going larger would require an audit of more code to make sure we - * aren't overflowing some other buffer. */ +/* + * Maximum size of an export name. The NBD spec requires a minimum of + * 256 and recommends that servers support up to 4096; all users use + * malloc so we can bump this constant without worry. + */ #define NBD_MAX_NAME_SIZE 256 /* Two types of reply structures */ diff --git a/nbd/server.c b/nbd/server.c index d8d1e62455..6bbeb98f82 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -324,18 +324,20 @@ static int nbd_opt_skip(NBDClient *client, size_t size, Error **errp) * uint32_t len (<= NBD_MAX_NAME_SIZE) * len bytes string (not 0-terminated) * - * @name should be enough to store NBD_MAX_NAME_SIZE+1. + * On success, @name will be allocated. * If @length is non-null, it will be set to the actual string length. * * Return -errno on I/O error, 0 if option was completely handled by * sending a reply about inconsistent lengths, or 1 on success. */ -static int nbd_opt_read_name(NBDClient *client, char *name, uint32_t *length, +static int nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length, Error **errp) { int ret; uint32_t len; + g_autofree char *local_name = NULL; + *name = NULL; ret = nbd_opt_read(client, &len, sizeof(len), errp); if (ret <= 0) { return ret; @@ -347,15 +349,17 @@ static int nbd_opt_read_name(NBDClient *client, char *name, uint32_t *length, "Invalid name length: %" PRIu32, len); } - ret = nbd_opt_read(client, name, len, errp); + local_name = g_malloc(len + 1); + ret = nbd_opt_read(client, local_name, len, errp); if (ret <= 0) { return ret; } - name[len] = '\0'; + local_name[len] = '\0'; if (length) { *length = len; } + *name = g_steal_pointer(&local_name); return 1; } @@ -427,7 +431,7 @@ static void nbd_check_meta_export(NBDClient *client) static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes, Error **errp) { - char name[NBD_MAX_NAME_SIZE + 1]; + g_autofree char *name = NULL; char buf[NBD_REPLY_EXPORT_NAME_SIZE] = ""; size_t len; int ret; @@ -441,10 +445,11 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes, [10 .. 133] reserved (0) [unless no_zeroes] */ trace_nbd_negotiate_handle_export_name(); - if (client->optlen >= sizeof(name)) { + if (client->optlen > NBD_MAX_NAME_SIZE) { error_setg(errp, "Bad length received"); return -EINVAL; } + name = g_malloc(client->optlen + 1); if (nbd_read(client->ioc, name, client->optlen, "export name", errp) < 0) { return -EIO; } @@ -533,7 +538,7 @@ static int nbd_reject_length(NBDClient *client, bool fatal, Error **errp) static int nbd_negotiate_handle_info(NBDClient *client, Error **errp) { int rc; - char name[NBD_MAX_NAME_SIZE + 1]; + g_autofree char *name = NULL; NBDExport *exp; uint16_t requests; uint16_t request; @@ -551,7 +556,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, Error **errp) 2 bytes: N, number of requests (can be 0) N * 2 bytes: N requests */ - rc = nbd_opt_read_name(client, name, &namelen, errp); + rc = nbd_opt_read_name(client, &name, &namelen, errp); if (rc <= 0) { return rc; } @@ -957,7 +962,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client, NBDExportMetaContexts *meta, Error **errp) { int ret; - char export_name[NBD_MAX_NAME_SIZE + 1]; + g_autofree char *export_name = NULL; NBDExportMetaContexts local_meta; uint32_t nb_queries; int i; @@ -976,7 +981,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client, memset(meta, 0, sizeof(*meta)); - ret = nbd_opt_read_name(client, export_name, NULL, errp); + ret = nbd_opt_read_name(client, &export_name, NULL, errp); if (ret <= 0) { return ret; }