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netinet: prevent NULL pointer dereference in in_aifaddr_ioctl()

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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
This commit is contained in:
Artem Khramov 2021-08-24 17:26:35 +03:00 committed by Warner Losh
parent 26d79d40a7
commit 620cf65c2b
1 changed files with 1 additions and 1 deletions
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2
sys/netinet/in.c
View file

@ -376,7 +376,7 @@ in_aifaddr_ioctl(u_long cmd, caddr_t data, struct ifnet *ifp, struct thread *td)
(dstaddr->sin_len != sizeof(struct sockaddr_in) ||
dstaddr->sin_addr.s_addr == INADDR_ANY))
return (EDESTADDRREQ);
if (vhid > 0 && carp_attach_p == NULL)
if (vhid != 0 && carp_attach_p == NULL)
return (EPROTONOSUPPORT);
/*