Message ID | 20210729093420.14092-1-julien@xen.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | tools/xenstored: Fix off-by-one in dump_state_nodes() | expand |
On 29.07.21 11:34, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > The maximum path length supported by Xenstored protocol is > XENSTORE_ABS_PATH_MAX (i.e 3072). This doesn't take into account the > NUL at the end of the path. > > However, the code to dump the nodes will allocate a buffer > of XENSTORE_ABS_PATH. As a result it may not be possible to live-update > if there is a node name of XENSTORE_ABS_PATH. > > Fix it by allocating a buffer of XENSTORE_ABS_PATH_MAX + 1 characters. > > Take the opportunity to pass the max length of the buffer as a > parameter of dump_state_node_tree(). This will be clearer that the > check in the function is linked to the allocation in dump_state_nodes(). > > Signed-off-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Juergen Gross <jgross@suse.com> > > --- > > This was spotted when backporting Live-Update to 4.11 because the > commit 924bf8c793 "tools/xenstore: rework path length check" is > not present. On the latest upstream, this is looks more a latent bug > because I didn't manage to create such large node. Yes, the path length is limited to "/local/domain/<id>/" + the max relative path length. Juergen
Julien Grall writes ("[PATCH] tools/xenstored: Fix off-by-one in dump_state_nodes()"): > The maximum path length supported by Xenstored protocol is > XENSTORE_ABS_PATH_MAX (i.e 3072). This doesn't take into account the > NUL at the end of the path. ... Julien Grall writes ("[PATCH] tools/xenstored: Propagate correctly the error message from lu_start()"): > lu_start() will only set errno when it returns NULL. For all the > other cases, the value is unknown. Thanks, and to Juergen for the reviews. Pushed. Ian.
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c index 16c856730c55..0d4c73d6e20c 100644 --- a/tools/xenstore/xenstored_core.c +++ b/tools/xenstore/xenstored_core.c @@ -2574,7 +2574,8 @@ const char *dump_state_node_perms(FILE *fp, const struct xs_permissions *perms, return NULL; } -static const char *dump_state_node_tree(FILE *fp, char *path) +static const char *dump_state_node_tree(FILE *fp, char *path, + unsigned int path_max_len) { unsigned int pathlen, childlen, p = 0; struct xs_state_record_header head; @@ -2642,10 +2643,10 @@ static const char *dump_state_node_tree(FILE *fp, char *path) } while (p < hdr->childlen) { childlen = strlen(child) + 1; - if (pathlen + childlen > XENSTORE_ABS_PATH_MAX) + if (pathlen + childlen > path_max_len) return "Dump node path length error"; strcpy(path + pathlen, child); - ret = dump_state_node_tree(fp, path); + ret = dump_state_node_tree(fp, path, path_max_len); if (ret) return ret; p += childlen; @@ -2661,13 +2662,13 @@ const char *dump_state_nodes(FILE *fp, const void *ctx) { char *path; - path = talloc_size(ctx, XENSTORE_ABS_PATH_MAX); + path = talloc_size(ctx, XENSTORE_ABS_PATH_MAX + 1); if (!path) return "Path buffer allocation error"; strcpy(path, "/"); - return dump_state_node_tree(fp, path); + return dump_state_node_tree(fp, path, XENSTORE_ABS_PATH_MAX + 1); } void read_state_global(const void *ctx, const void *state)