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From: Andrew Ballance <andrewjballance@gmail.com>
To: syzbot+39b2fb0f2638669008ec@syzkaller.appspotmail.com
Cc: almaz.alexandrovich@paragon-software.com,
	linux-kernel@vger.kernel.org,
	ntfs3@lists.linux.dev,
	syzkaller-bugs@googlegroups.com,
	skhan@linuxfoundation.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Andrew Ballance <andrewjballance@gmail.com>
Subject: [PATCH] ntfs3: check if more than chunk-size bytes are written
Date: Wed, 15 May 2024 07:38:33 -0500
Message-ID: <20240515123946.874688-1-andrewjballance@gmail.com>
In-Reply-To: <00000000000077d29606186c5e99@google.com>
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#syz test

a incorrectly formatted chunk may decompress into
more than LZNT_CHUNK_SIZE bytes and a index out of bounds
will occur in s_max_off.

Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
---
 fs/ntfs3/lznt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/lznt.c b/fs/ntfs3/lznt.c
index 4aae598d6d88..fdc9b2ebf341 100644
--- a/fs/ntfs3/lznt.c
+++ b/fs/ntfs3/lznt.c
@@ -236,6 +236,9 @@ static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr,
 
 	/* Do decompression until pointers are inside range. */
 	while (up < unc_end && cmpr < cmpr_end) {
+		// return err if more than LZNT_CHUNK_SIZE bytes are written
+		if (up - unc > LZNT_CHUNK_SIZE)
+			return -EINVAL;
 		/* Correct index */
 		while (unc + s_max_off[index] < up)
 			index += 1;
-- 
2.45.0