Patrick Georgi (pgeorgi@google.com) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/13672
-gerrit
commit a54672ba73da6d834dbe3ee88de0353b39d89cb2 Author: Patrick Georgi pgeorgi@chromium.org Date: Wed Feb 10 18:07:52 2016 +0100
util/cbfstool: Improve heuristic for cbfs header pointer protection
cbfstool has a routine to deal with old images that may encourage it to overwrite the master header. That routine is triggered for "cbfstool add-master-header" prepared images even though these are not at risk, and - worse - destroys the chain structure (through a negative file length), so avoid touching such images.
Change-Id: I9d0bbe3e6300b9b9f3e50347737d1850f83ddad8 Signed-off-by: Patrick Georgi pgeorgi@chromium.org --- util/cbfstool/cbfs_image.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/util/cbfstool/cbfs_image.c b/util/cbfstool/cbfs_image.c index 314ea57..65d7f7c 100644 --- a/util/cbfstool/cbfs_image.c +++ b/util/cbfstool/cbfs_image.c @@ -110,6 +110,9 @@ static int cbfs_fix_legacy_size(struct cbfs_image *image, char *hdr_loc) // A bug in old cbfstool may produce extra few bytes (by alignment) and // cause cbfstool to overwrite things after free space -- which is // usually CBFS header on x86. We need to workaround that. + // Except when the last file is smaller than the header alignment, + // since that's a pretty good clue that the last file exists to guard + // the header pointer (and the master header is in a file, too).
struct cbfs_file *entry, *first = NULL, *last = NULL; for (first = entry = cbfs_find_first_entry(image); @@ -118,7 +121,8 @@ static int cbfs_fix_legacy_size(struct cbfs_image *image, char *hdr_loc) last = entry; } if ((char *)first < (char *)hdr_loc && - (char *)entry > (char *)hdr_loc) { + (char *)entry > (char *)hdr_loc && + (ntohl(last->len) > image->header.align)) { WARN("CBFS image was created with old cbfstool with size bug. " "Fixing size in last entry...\n"); last->len = htonl(ntohl(last->len) - image->header.align);