From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
Andrew Morton <akpm@linux-foundation.org>,
Namjae Jeon <linkinjeon@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>
Cc: syzbot <syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com>,
syzkaller-bugs@googlegroups.com, ntfs3@lists.linux.dev,
LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] fs/ntfs3: fix negative shift size in true_sectors_per_clst()
Date: Wed, 21 Sep 2022 00:59:27 +0900 [thread overview]
Message-ID: <4b37f037-3b10-b4e4-0644-73441c8fa0af@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <000000000000f8b5ef05dd25b963@google.com>
syzbot is reporting shift-out-of-bounds in true_sectors_per_clst() [1], for
commit a3b774342fa752a5 ("fs/ntfs3: validate BOOT sectors_per_clusters")
did not address that (0 - boot->sectors_per_clusters) < 0 because "u8" was
chosen for type of boot->sectors_per_clusters because 0x80 needs to be
positive in order to support 64K clusters. Use "s8" cast in order to make
sure that (0 - (s8) boot->sectors_per_clusters) > 0.
Link: https://syzkaller.appspot.com/bug?extid=1631f09646bc214d2e76 [1]
Reported-by: syzbot <syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com>
Fixes: a3b774342fa752a5 ("fs/ntfs3: validate BOOT sectors_per_clusters")
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 47012c9bf505..c7ffd21fb255 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -672,7 +672,7 @@ static u32 true_sectors_per_clst(const struct NTFS_BOOT *boot)
if (boot->sectors_per_clusters <= 0x80)
return boot->sectors_per_clusters;
if (boot->sectors_per_clusters >= 0xf4) /* limit shift to 2MB max */
- return 1U << (0 - boot->sectors_per_clusters);
+ return 1U << (0 - (s8) boot->sectors_per_clusters);
return -EINVAL;
}
--
2.18.4
next prev parent reply other threads:[~2022-09-20 16:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 8:16 [syzbot] UBSAN: shift-out-of-bounds in ntfs_fill_super syzbot
2022-04-21 8:37 ` syzbot
2022-04-21 12:29 ` syzbot
2022-09-20 15:59 ` Tetsuo Handa [this message]
2022-09-23 0:38 ` [PATCH] fs/ntfs3: fix negative shift size in true_sectors_per_clst() Randy Dunlap
2022-09-23 0:47 ` Joe Perches
2022-09-23 1:14 ` Randy Dunlap
2022-09-23 9:59 ` Dan Carpenter
2022-09-23 1:25 ` Tetsuo Handa
2022-09-23 11:58 ` Aleksandr Nogikh
2022-09-23 14:35 ` Tetsuo Handa
2022-09-24 11:58 ` Aleksandr Nogikh
2022-09-24 12:03 ` Aleksandr Nogikh
2022-09-23 11:58 ` Konstantin Komarov
2022-09-23 16:07 ` Randy Dunlap
2022-09-30 16:34 ` Konstantin Komarov
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