From: Michael Tokarev <mjt@tls.msk.ru>
Date: Sun, 29 Dec 2024 21:08:50 +0000 (+0300)
Subject: Revert "vvfat: fix ubsan issue in create_long_filename"
X-Git-Tag: v10.0.0-rc0~102^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d8d17d2bf6181cdc9b8ef3db862006ddb6af12d4;p=thirdparty%2Fqemu.git

Revert "vvfat: fix ubsan issue in create_long_filename"

This reverts commit 0cb3ff7c22671aa1e1e227318799ccf6762c3bea.

The original code was right in that long name in LFN directory
entry uses other parts of the entry for the name too, not just
the original "name" field.  So it is wrong to limit the offset
to be within the name field.  Some other mechanism is needed
to fix the ubsan report and whole messy usage of bytes past the
given field.

Reported-by: Volker Rümelin <vr_qemu@t-online.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---

diff --git a/block/vvfat.c b/block/vvfat.c
index f2eafaa9234..8ffe8b3b9bf 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -426,10 +426,6 @@ static direntry_t *create_long_filename(BDRVVVFATState *s, const char *filename)
         else if(offset<22) offset=14+offset-10;
         else offset=28+offset-22;
         entry=array_get(&(s->directory),s->directory.next-1-(i/26));
-        /* ensure we don't write anything past entry->name */
-        if (offset >= sizeof(entry->name)) {
-            continue;
-        }
         if (i >= 2 * length + 2) {
             entry->name[offset] = 0xff;
         } else if (i % 2 == 0) {