From: Omar Polo <op@omarpolo.com>
Subject: check for size_t overflow when mapping memory
To: gameoftrees@openbsd.org
Date: Mon, 24 Oct 2022 21:57:38 +0200

diff below ensures that every time we call mmap(2) the size argument
effectively less than SIZE_MAX.  In some cases this is a no-op since
filesize is currently size_t and so we've potentially already
truncated the value.  In a follow-up commit i'd like to turn the
`filesize' field in the structs got_pack and packidx from size_t to
off_t, so these checks will start to work.


diff 933f287a77cf1c9dced8ed3afbf3850f5c0c1bb3 90ac69281429b4caf05f7b3617e0acabdc062028
commit - 933f287a77cf1c9dced8ed3afbf3850f5c0c1bb3
commit + 90ac69281429b4caf05f7b3617e0acabdc062028
blob - f8e685448165384cfc578c0f089b4aa6fb6219c8
blob + 7f2a014edb74884a7f92a43fb66ec78eb24e3228
--- lib/object.c
+++ lib/object.c
@@ -926,7 +926,10 @@ got_object_raw_alloc(struct got_raw_object **obj, uint
     size_t hdrlen, off_t size)
 {
 	const struct got_error *err = NULL;
+	off_t tot;
 
+	tot = hdrlen + size;
+
 	*obj = calloc(1, sizeof(**obj));
 	if (*obj == NULL) {
 		err = got_error_from_errno("calloc");
@@ -944,13 +947,15 @@ got_object_raw_alloc(struct got_raw_object **obj, uint
 			goto done;
 		}
 
-		if (sb.st_size != hdrlen + size) {
+		if (sb.st_size != tot) {
 			err = got_error(GOT_ERR_PRIVSEP_LEN);
 			goto done;
 		}
 #ifndef GOT_PACK_NO_MMAP
-		if (hdrlen + size > 0) {
-			(*obj)->data = mmap(NULL, hdrlen + size, PROT_READ,
+		(*obj)->fd = *outfd;
+		*outfd = -1;
+		if (tot > 0 && tot < SIZE_MAX) {
+			(*obj)->data = mmap(NULL, tot, PROT_READ,
 			    MAP_PRIVATE, *outfd, 0);
 			if ((*obj)->data == MAP_FAILED) {
 				if (errno != ENOMEM) {
@@ -958,9 +963,6 @@ got_object_raw_alloc(struct got_raw_object **obj, uint
 					goto done;
 				}
 				(*obj)->data = NULL;
-			} else {
-				(*obj)->fd = *outfd;
-				*outfd = -1;
 			}
 		}
 #endif
blob - becc8ffd68217466f0bad6d811196c0d7137e4df
blob + 0b79146e747f73787b2ee568b7fb74c517ce1d9e
--- lib/pack.c
+++ lib/pack.c
@@ -392,13 +392,15 @@ got_packidx_open(struct got_packidx **packidx,
 	}
 
 #ifndef GOT_PACK_NO_MMAP
-	p->map = mmap(NULL, p->len, PROT_READ, MAP_PRIVATE, p->fd, 0);
-	if (p->map == MAP_FAILED) {
-		if (errno != ENOMEM) {
-			err = got_error_from_errno("mmap");
-			goto done;
+	if (p->len < SIZE_MAX) {
+		p->map = mmap(NULL, p->len, PROT_READ, MAP_PRIVATE, p->fd, 0);
+		if (p->map == MAP_FAILED) {
+			if (errno != ENOMEM) {
+				err = got_error_from_errno("mmap");
+				goto done;
+			}
+			p->map = NULL; /* fall back to read(2) */
 		}
-		p->map = NULL; /* fall back to read(2) */
 	}
 #endif
 
@@ -1036,7 +1038,6 @@ resolve_offset_delta(struct got_delta_chain *deltas,
 resolve_offset_delta(struct got_delta_chain *deltas,
     struct got_packidx *packidx, struct got_pack *pack, off_t delta_offset,
     size_t tslen, int delta_type, size_t delta_size, unsigned int recursion)
-
 {
 	const struct got_error *err;
 	off_t base_offset;
blob - b07bf0c9c711997031a7d3afa3388a27527ef2db
blob + 7372c43fc3a9bd8d47fb3d868c90311eb3c51451
--- lib/repository.c
+++ lib/repository.c
@@ -1427,15 +1427,18 @@ got_repo_cache_pack(struct got_pack **packp, struct go
 	if (err)
 		goto done;
 
+	pack->map = NULL;
 #ifndef GOT_PACK_NO_MMAP
-	pack->map = mmap(NULL, pack->filesize, PROT_READ, MAP_PRIVATE,
-	    pack->fd, 0);
-	if (pack->map == MAP_FAILED) {
-		if (errno != ENOMEM) {
-			err = got_error_from_errno("mmap");
-			goto done;
+	if (pack->filesize < SIZE_MAX) {
+		pack->map = mmap(NULL, pack->filesize, PROT_READ, MAP_PRIVATE,
+		    pack->fd, 0);
+		if (pack->map == MAP_FAILED) {
+			if (errno != ENOMEM) {
+				err = got_error_from_errno("mmap");
+				goto done;
+			}
+			pack->map = NULL; /* fall back to read(2) */
 		}
-		pack->map = NULL; /* fall back to read(2) */
 	}
 #endif
 done:
blob - 8a38382357c6aeb5b642965a26a50d9a6621d34e
blob + e914ae79dd30bfd6591ea94dfadb6d91ddd80c65
--- libexec/got-index-pack/got-index-pack.c
+++ libexec/got-index-pack/got-index-pack.c
@@ -183,10 +183,12 @@ main(int argc, char **argv)
 	}
 
 #ifndef GOT_PACK_NO_MMAP
-	pack.map = mmap(NULL, pack.filesize, PROT_READ, MAP_PRIVATE,
-	    pack.fd, 0);
-	if (pack.map == MAP_FAILED)
-		pack.map = NULL; /* fall back to read(2) */
+	if (pack.filesize < SIZE_MAX) {
+		pack.map = mmap(NULL, pack.filesize, PROT_READ, MAP_PRIVATE,
+		    pack.fd, 0);
+		if (pack.map == MAP_FAILED)
+			pack.map = NULL; /* fall back to read(2) */
+	}
 #endif
 	err = got_pack_index(&pack, idxfd, tmpfiles[0], tmpfiles[1],
 	    tmpfiles[2], pack_hash, send_index_pack_progress, &ibuf, &rl);
blob - 268ab18c5371e622b7f9c3a62c9a894a7050de85
blob + fd77f35cfff0c52c0cf09457929ce3c48d8470c8
--- libexec/got-read-pack/got-read-pack.c
+++ libexec/got-read-pack/got-read-pack.c
@@ -1146,9 +1146,11 @@ receive_packidx(struct got_packidx **packidx, struct i
 	}
 
 #ifndef GOT_PACK_NO_MMAP
-	p->map = mmap(NULL, p->len, PROT_READ, MAP_PRIVATE, p->fd, 0);
-	if (p->map == MAP_FAILED)
-		p->map = NULL; /* fall back to read(2) */
+	if (p->len < SIZE_MAX) {
+		p->map = mmap(NULL, p->len, PROT_READ, MAP_PRIVATE, p->fd, 0);
+		if (p->map == MAP_FAILED)
+			p->map = NULL; /* fall back to read(2) */
+	}
 #endif
 	err = got_packidx_init_hdr(p, 1, ipackidx.packfile_size);
 done:
@@ -1874,10 +1876,12 @@ receive_pack(struct got_pack **packp, struct imsgbuf *
 		goto done;
 
 #ifndef GOT_PACK_NO_MMAP
-	pack->map = mmap(NULL, pack->filesize, PROT_READ, MAP_PRIVATE,
-	    pack->fd, 0);
-	if (pack->map == MAP_FAILED)
-		pack->map = NULL; /* fall back to read(2) */
+	if (pack->filesize < SIZE_MAX) {
+		pack->map = mmap(NULL, pack->filesize, PROT_READ, MAP_PRIVATE,
+		    pack->fd, 0);
+		if (pack->map == MAP_FAILED)
+			pack->map = NULL; /* fall back to read(2) */
+	}
 #endif
 done:
 	if (err) {