Re: [PATCH iproute2] libnetlink: check error handler is present before a call

[Roi Dayan <roid@nvidia.com>]

On 2021-07-11 2:15 PM, Alexander Mikhalitsyn wrote:
> Fix nullptr dereference of errhndlr from rtnl_dump_filter_arg
> struct in rtnl_dump_done and rtnl_dump_error functions.
> 
> Fixes: 459ce6e3d792 ("ip route: ignore ENOENT during save if RT_TABLE_MAIN is being dumped")
> Cc: Stephen Hemminger <stephen@networkplumber.org>
> Cc: Roi Dayan <roid@nvidia.com>
> Cc: Alexander Mikhalitsyn <alexander@mihalicyn.com>
> Reported-by: Roi Dayan <roid@nvidia.com>
> Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
> ---
>   lib/libnetlink.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index e9b8c3bd..d068dbe2 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -686,7 +686,7 @@ static int rtnl_dump_done(struct nlmsghdr *h,
>   	if (len < 0) {
>   		errno = -len;
>   
> -		if (a->errhndlr(h, a->arg2) & RTNL_SUPPRESS_NLMSG_DONE_NLERR)
> +		if (a->errhndlr && (a->errhndlr(h, a->arg2) & RTNL_SUPPRESS_NLMSG_DONE_NLERR))
>   			return 0;
>   
>   		/* check for any messages returned from kernel */
> @@ -729,7 +729,7 @@ static int rtnl_dump_error(const struct rtnl_handle *rth,
>   		     errno == EOPNOTSUPP))
>   			return -1;
>   
> -		if (a->errhndlr(h, a->arg2) & RTNL_SUPPRESS_NLMSG_ERROR_NLERR)
> +		if (a->errhndlr && (a->errhndlr(h, a->arg2) & RTNL_SUPPRESS_NLMSG_ERROR_NLERR))
>   			return 0;
>   
>   		if (!(rth->flags & RTNL_HANDLE_F_SUPPRESS_NLERR))
> 

that was quick. was about to send the exact same patch :)
so tested as well. thanks!

Reviewed-by: Roi Dayan <roid@nvidia.com>