libflashrom/fmap: Don't use off_t for flash offsets

off_t is a special POSIX type that is used to represent file offsets in
certain APIs (e.g. lseek(), mmap()), and should not be reused to
represent anything else (such as flash offsets). In particular, the
width of the type may change based on the definition of the
_FILE_OFFSET_BITS macro. Using such a type at the libflashrom interface
is particularly dangerous, because if a program is built with a
different _FILE_OFFSET_BITS value than libflashrom, the resulting ABI
corruption will cause very very nasty and confusing bugs. This patch
replaces all instances of off_t that are not related to file offsets
with (s)size_t.

BUG=b:219811851
TEST=`elogtool list` on cherry.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I68a386973f79ea634f63dfcd7d95a63400e1fdee
Reviewed-on: https://review.coreboot.org/c/flashrom/+/61943
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/fmap.c b/fmap.c
index 0236b621a..bd847bd0b 100644
--- a/fmap.c
+++ b/fmap.c
@@ -91,15 +91,15 @@ static int is_valid_fmap(const struct fmap *fmap)
  *         -1 to indicate that fmap was not found
  *         -2 to indicate fmap is truncated or exceeds buffer + len
  */
-static off_t fmap_lsearch(const uint8_t *buf, size_t len)
+static ssize_t fmap_lsearch(const uint8_t *buf, size_t len)
 {
-	off_t offset;
+	ssize_t offset;
 	bool fmap_found = 0;
 
 	if (len < sizeof(struct fmap))
 		return -1;
 
-	for (offset = 0; offset <= (off_t)(len - sizeof(struct fmap)); offset++) {
+	for (offset = 0; offset <= (ssize_t)(len - sizeof(struct fmap)); offset++) {
 		if (is_valid_fmap((struct fmap *)&buf[offset])) {
 			fmap_found = 1;
 			break;
@@ -131,7 +131,7 @@ static off_t fmap_lsearch(const uint8_t *buf, size_t len)
  */
 int fmap_read_from_buffer(struct fmap **fmap_out, const uint8_t *const buf, size_t len)
 {
-	off_t offset = fmap_lsearch(buf, len);
+	ssize_t offset = fmap_lsearch(buf, len);
 	if (offset < 0) {
 		msg_gdbg("Unable to find fmap in provided buffer.\n");
 		return 2;