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netmap: Fix TOCTOU vulnerability in nmreq_copyin

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The total size of the user-provided nmreq was first computed and then
trusted during the copyin. This might lead to kernel memory corruption
and escape from jails/containers.

Reported by: Lucas Leong (@_wmliang_) of Trend Micro Zero Day Initiative
Security: CVE-2022-23084
MFC after:	3 days
This commit is contained in:
Vincenzo Maffione 2022-03-16 06:58:50 +00:00
parent 694ea59c70
commit 3937299165
1 changed files with 17 additions and 34 deletions
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51
sys/dev/netmap/netmap.c
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@ -3362,11 +3362,10 @@ nmreq_opt_size_by_type(uint32_t nro_reqtype, uint64_t nro_size)
int
nmreq_copyin(struct nmreq_header *hdr, int nr_body_is_user)
{
size_t rqsz, optsz, bufsz, optbodysz;
size_t rqsz, optsz, bufsz;
int error = 0;
char *ker = NULL, *p;
struct nmreq_option **next, *src, **opt_tab;
struct nmreq_option buf;
uint64_t *ptrs;
if (hdr->nr_reserved) {
@ -3396,39 +3395,14 @@ nmreq_copyin(struct nmreq_header *hdr, int nr_body_is_user)
goto out_err;
}
bufsz = 2 * sizeof(void *) + rqsz +
NETMAP_REQ_OPT_MAX * sizeof(opt_tab);
/* compute the size of the buf below the option table.
* It must contain a copy of every received option structure.
* For every option we also need to store a copy of the user
* list pointer.
/*
* The buffer size must be large enough to store the request body,
* all the possible options and the additional user pointers
* (2+NETMAP_REQ_OPT_MAX). Note that the maximum size of body plus
* options can not exceed NETMAP_REQ_MAXSIZE;
*/
optsz = 0;
for (src = (struct nmreq_option *)(uintptr_t)hdr->nr_options; src;
src = (struct nmreq_option *)(uintptr_t)buf.nro_next)
{
error = copyin(src, &buf, sizeof(*src));
if (error)
goto out_err;
/* Validate nro_size to avoid integer overflow of optsz and bufsz. */
if (buf.nro_size > NETMAP_REQ_MAXSIZE) {
error = EMSGSIZE;
goto out_err;
}
optsz += sizeof(*src);
optbodysz = nmreq_opt_size_by_type(buf.nro_reqtype, buf.nro_size);
if (optbodysz > NETMAP_REQ_MAXSIZE) {
error = EMSGSIZE;
goto out_err;
}
optsz += optbodysz;
if (rqsz + optsz > NETMAP_REQ_MAXSIZE) {
error = EMSGSIZE;
goto out_err;
}
bufsz += sizeof(void *);
}
bufsz += optsz;
bufsz = (2 + NETMAP_REQ_OPT_MAX) * sizeof(void *) + NETMAP_REQ_MAXSIZE +
NETMAP_REQ_OPT_MAX * sizeof(opt_tab);
ker = nm_os_malloc(bufsz);
if (ker == NULL) {
@ -3466,6 +3440,7 @@ nmreq_copyin(struct nmreq_header *hdr, int nr_body_is_user)
error = copyin(src, opt, sizeof(*src));
if (error)
goto out_restore;
rqsz += sizeof(*src);
/* make a copy of the user next pointer */
*ptrs = opt->nro_next;
/* overwrite the user pointer with the in-kernel one */
@ -3509,6 +3484,14 @@ nmreq_copyin(struct nmreq_header *hdr, int nr_body_is_user)
/* copy the option body */
optsz = nmreq_opt_size_by_type(opt->nro_reqtype,
opt->nro_size);
/* check optsz and nro_size to avoid for possible integer overflows of rqsz */
if ((optsz > NETMAP_REQ_MAXSIZE) || (opt->nro_size > NETMAP_REQ_MAXSIZE)
|| (rqsz + optsz > NETMAP_REQ_MAXSIZE)
|| (optsz > 0 && rqsz + optsz <= rqsz)) {
error = EMSGSIZE;
goto out_restore;
}
rqsz += optsz;
if (optsz) {
/* the option body follows the option header */
error = copyin(src + 1, p, optsz);