On Tue, 9 Jul 2019 22:40:40 +0200
Matteo Croce <mcr...@redhat.com> wrote:
> iproute has an utility function which checks if a string is a prefix for
> another one, to allow use of abbreviated commands, e.g. 'addr' or 'a'
> instead of 'address'.
>
> This routine unfortunately considers an empty string as prefix
> of any pattern, leading to undefined behaviour when an empty
> argument is passed to ip:
>
> # ip ''
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group
> default qlen 1000
> link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
> inet 127.0.0.1/8 scope host lo
> valid_lft forever preferred_lft forever
> inet6 ::1/128 scope host
> valid_lft forever preferred_lft forever
>
> # tc ''
> qdisc noqueue 0: dev lo root refcnt 2
>
> # ip address add 192.0.2.0/24 '' 198.51.100.1 dev dummy0
> # ip addr show dev dummy0
> 6: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default
> qlen 1000
> link/ether 02:9d:5e:e9:3f:c0 brd ff:ff:ff:ff:ff:ff
> inet 192.0.2.0/24 brd 198.51.100.1 scope global dummy0
> valid_lft forever preferred_lft forever
>
> Rewrite matches() so it takes care of an empty input, and doesn't
> scan the input strings three times: the actual implementation
> does 2 strlen and a memcpy to accomplish the same task.
>
> Signed-off-by: Matteo Croce <mcr...@redhat.com>
> ---
> include/utils.h | 2 +-
> lib/utils.c | 14 +++++++++-----
> 2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/include/utils.h b/include/utils.h
> index 927fdc17..f4d12abb 100644
> --- a/include/utils.h
> +++ b/include/utils.h
> @@ -198,7 +198,7 @@ int nodev(const char *dev);
> int check_ifname(const char *);
> int get_ifname(char *, const char *);
> const char *get_ifname_rta(int ifindex, const struct rtattr *rta);
> -int matches(const char *arg, const char *pattern);
> +int matches(const char *prefix, const char *string);
> int inet_addr_match(const inet_prefix *a, const inet_prefix *b, int bits);
> int inet_addr_match_rta(const inet_prefix *m, const struct rtattr *rta);
>
> diff --git a/lib/utils.c b/lib/utils.c
> index be0f11b0..73ce19bb 100644
> --- a/lib/utils.c
> +++ b/lib/utils.c
> @@ -887,13 +887,17 @@ const char *get_ifname_rta(int ifindex, const struct
> rtattr *rta)
> return name;
> }
>
> -int matches(const char *cmd, const char *pattern)
> +/* Check if 'prefix' is a non empty prefix of 'string' */
> +int matches(const char *prefix, const char *string)
> {
> - int len = strlen(cmd);
> + if (!*prefix)
> + return 1;
> + while(*string && *prefix == *string) {
> + prefix++;
> + string++;
> + }
>
> - if (len > strlen(pattern))
> - return -1;
> - return memcmp(pattern, cmd, len);
> + return *prefix;
> }
>
> int inet_addr_match(const inet_prefix *a, const inet_prefix *b, int bits)
ERROR: space required before the open parenthesis '('
#134: FILE: lib/utils.c:895:
+ while(*string && *prefix == *string) {
total: 1 errors, 1 warnings, 30 lines checked
The empty prefix string is a bug and should not be allowed.
Also return value should be same as old code (yours isn't).
