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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	ZhangPeng <zhangpeng362@huawei.com>,
	Viacheslav Dubeyko <slava@dubeyko.com>,
	syzbot+dc3b1cf9111ab5fe98e7@syzkaller.appspotmail.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 138/731] hfs: Fix OOB Write in hfs_asc2mac
Date: Wed, 28 Dec 2022 15:34:05 +0100
Message-Id: <20221228144300.549648285@linuxfoundation.org>
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From: ZhangPeng <zhangpeng362@huawei.com>

[ Upstream commit c53ed55cb275344086e32a7080a6b19cb183650b ]

Syzbot reported a OOB Write bug:

loop0: detected capacity change from 0 to 64
==================================================================
BUG: KASAN: slab-out-of-bounds in hfs_asc2mac+0x467/0x9a0
fs/hfs/trans.c:133
Write of size 1 at addr ffff88801848314e by task syz-executor391/3632

Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 print_address_description+0x74/0x340 mm/kasan/report.c:284
 print_report+0x107/0x1f0 mm/kasan/report.c:395
 kasan_report+0xcd/0x100 mm/kasan/report.c:495
 hfs_asc2mac+0x467/0x9a0 fs/hfs/trans.c:133
 hfs_cat_build_key+0x92/0x170 fs/hfs/catalog.c:28
 hfs_lookup+0x1ab/0x2c0 fs/hfs/dir.c:31
 lookup_open fs/namei.c:3391 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x10e6/0x2df0 fs/namei.c:3710
 do_filp_open+0x264/0x4f0 fs/namei.c:3740

If in->len is much larger than HFS_NAMELEN(31) which is the maximum
length of an HFS filename, a OOB write could occur in hfs_asc2mac(). In
that case, when the dst reaches the boundary, the srclen is still
greater than 0, which causes a OOB write.
Fix this by adding a check on dstlen in while() before writing to dst
address.

Link: https://lkml.kernel.org/r/20221202030038.1391945-1-zhangpeng362@huawei.com
Fixes: 328b92278650 ("[PATCH] hfs: NLS support")
Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Reported-by: <syzbot+dc3b1cf9111ab5fe98e7@syzkaller.appspotmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/hfs/trans.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfs/trans.c b/fs/hfs/trans.c
index 39f5e343bf4d..fdb0edb8a607 100644
--- a/fs/hfs/trans.c
+++ b/fs/hfs/trans.c
@@ -109,7 +109,7 @@ void hfs_asc2mac(struct super_block *sb, struct hfs_name *out, const struct qstr
 	if (nls_io) {
 		wchar_t ch;
 
-		while (srclen > 0) {
+		while (srclen > 0 && dstlen > 0) {
 			size = nls_io->char2uni(src, srclen, &ch);
 			if (size < 0) {
 				ch = '?';
-- 
2.35.1