K 10
svn:author
V 3
imp
K 8
svn:date
V 27
2021-09-12T18:33:56.565132Z
K 7
svn:log
V 1576
netinet: prevent NULL pointer dereference in in_aifaddr_ioctl()

It appears that maliciously crafted ifaliasreq can lead to NULL
pointer dereference in in_aifaddr_ioctl(). In order to replicate
that, one needs to

1. Ensure that carp(4) is not loaded

2. Issue SIOCAIFADDR call setting ifra_vhid field of the request
   to a negative value.

A repro code would look like this.

int main() {
    struct ifaliasreq req;
    struct sockaddr_in sin, mask;
    int fd, error;

    bzero(&sin, sizeof(struct sockaddr_in));
    bzero(&mask, sizeof(struct sockaddr_in));

    sin.sin_len = sizeof(struct sockaddr_in);
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr("192.168.88.2");

    mask.sin_len = sizeof(struct sockaddr_in);
    mask.sin_family = AF_INET;
    mask.sin_addr.s_addr = inet_addr("255.255.255.0");

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd < 0)
        return (-1);

    memset(&req, 0, sizeof(struct ifaliasreq));
    strlcpy(req.ifra_name, "lo0", sizeof(req.ifra_name));
    memcpy(&req.ifra_addr, &sin, sin.sin_len);
    memcpy(&req.ifra_mask, &mask, mask.sin_len);
    req.ifra_vhid = -1;

    return ioctl(fd, SIOCAIFADDR, (char *)&req);
}

To fix, discard both positive and negative vhid values in
in_aifaddr_ioctl, if carp(4) is not loaded. This prevents NULL pointer
dereference and kernel panic.

Reviewed by:	imp@
Pull Request:	https://github.com/freebsd/freebsd-src/pull/530

(cherry picked from commit 620cf65c2bc4035a07e1152da419a4e60d36ff9b)

Git Hash:   7a26124388ef3ce76ad7b9d8c45d20f222d73a41
Git Author: akhramov@pm.me
END