On Thu, Dec 13, 2012 at 11:23:42AM +1100, NeilBrown wrote:
>
> The is_subdirectory() function checks if a given 'child' is a subdirectory
> of the given 'parent'.
> However it always fails if 'parent' == "/" (because 'child' doesn't begin
> with 'parent' followed by "/").
>
> So change is_subdirectory() to special-case "/".
Might be slightly more elegant to deal with this as a case of a parent
directory with a terminating "/" rather than as a special case, and that
might make this a little more robust. E.g.:
size_t l = strlen(parent);
while (l && parent[l-1] == '/')
l--;
return (l <= strlen(child))
&& strncmp(parent, child, l) == 0
&& (child[l] == '/' || child[l] == '\0');
?
--b.
>
> subexport() also tests if one directory is a subdirectory of the
> other, and contains the same bug. So change it to use is_subdirectory().
>
> Finally, move is_subdirectory() and related path_matches() and
> export_matches() earlier in the file to avoid a forward-reference.
>
> This patch fixes a bug wherein if you export "/" with 'crossmnt', the
> crossmnt flag is ineffective and you can only access the root
> filesystem, not any descendants.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
>
> diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
> index 3853bb6..45012be 100644
> --- a/utils/mountd/cache.c
> +++ b/utils/mountd/cache.c
> @@ -343,6 +343,30 @@ static char *next_mnt(void **v, char *p)
> return me->mnt_dir;
> }
>
> +static int is_subdirectory(char *child, char *parent)
> +{
> + size_t l = strlen(parent);
> +
> + if (strcmp(parent, "/") == 0)
> + return 1;
> +
> + return strcmp(child, parent) == 0
> + || (strncmp(child, parent, l) == 0 && child[l] == '/');
> +}
> +
> +static int path_matches(nfs_export *exp, char *path)
> +{
> + if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
> + return is_subdirectory(path, exp->m_export.e_path);
> + return strcmp(path, exp->m_export.e_path) == 0;
> +}
> +
> +static int
> +export_matches(nfs_export *exp, char *dom, char *path, struct addrinfo *ai)
> +{
> + return path_matches(exp, path) && client_matches(exp, dom, ai);
> +}
> +
> /* True iff e1 is a child of e2 and e2 has crossmnt set: */
> static bool subexport(struct exportent *e1, struct exportent *e2)
> {
> @@ -350,8 +374,7 @@ static bool subexport(struct exportent *e1, struct exportent *e2)
> size_t l2 = strlen(p2);
>
> return e2->e_flags & NFSEXP_CROSSMOUNT
> - && strncmp(p1, p2, l2) == 0
> - && p1[l2] == '/';
> + && is_subdirectory(p1, p2);
> }
>
> struct parsed_fsid {
> @@ -752,27 +775,6 @@ static int dump_to_cache(FILE *f, char *domain, char *path, struct exportent *ex
> return qword_eol(f);
> }
>
> -static int is_subdirectory(char *child, char *parent)
> -{
> - size_t l = strlen(parent);
> -
> - return strcmp(child, parent) == 0
> - || (strncmp(child, parent, l) == 0 && child[l] == '/');
> -}
> -
> -static int path_matches(nfs_export *exp, char *path)
> -{
> - if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
> - return is_subdirectory(path, exp->m_export.e_path);
> - return strcmp(path, exp->m_export.e_path) == 0;
> -}
> -
> -static int
> -export_matches(nfs_export *exp, char *dom, char *path, struct addrinfo *ai)
> -{
> - return path_matches(exp, path) && client_matches(exp, dom, ai);
> -}
> -
> static nfs_export *
> lookup_export(char *dom, char *path, struct addrinfo *ai)
> {
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