git: 725c70d8153f - stable/11 - netmap: Fix TOCTOU vulnerability in nmreq_copyin

The branch stable/11 has been updated by vmaffione:

URL: https://cgit.FreeBSD.org/src/commit/?id=725c70d8153f4bddf95bdd07e2c7b4b9399643f6

commit 725c70d8153f4bddf95bdd07e2c7b4b9399643f6
Author:     Vincenzo Maffione <vmaffione@FreeBSD.org>
AuthorDate: 2022-03-16 06:58:50 +0000
Commit:     Vincenzo Maffione <vmaffione@FreeBSD.org>
CommitDate: 2022-03-30 22:08:32 +0000

    netmap: Fix TOCTOU vulnerability in nmreq_copyin
    
    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
    
    (cherry picked from commit 393729916564ed13f966e09129a24e6931898d12)
---
 sys/dev/netmap/netmap.c | 46 ++++++++++++++++++----------------------------
 1 file changed, 18 insertions(+), 28 deletions(-)

diff --git a/sys/dev/netmap/netmap.c b/sys/dev/netmap/netmap.c
index 0c060219ff23..ab2c1b760d6a 100644
--- a/sys/dev/netmap/netmap.c
+++ b/sys/dev/netmap/netmap.c
@@ -2987,11 +2987,10 @@ 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;
-	struct nmreq_option buf;
 	uint64_t *ptrs;
 
 	if (hdr->nr_reserved) {
@@ -3021,32 +3020,14 @@ nmreq_copyin(struct nmreq_header *hdr, int nr_body_is_user)
 		goto out_err;
 	}
 
-	bufsz = 2 * sizeof(void *) + rqsz;
-	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 += optsz + sizeof(void *);
-	}
+	/*
+	 * 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;
+	 */
+	bufsz = (2 + NETMAP_REQ_OPT_SYNC_KLOOP_MODE + 1) * sizeof(void *)
+	    + NETMAP_REQ_MAXSIZE;
 
 	ker = nm_os_malloc(bufsz);
 	if (ker == NULL) {
@@ -3081,6 +3062,7 @@ 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 */
@@ -3096,6 +3078,14 @@ 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);