linux-kernel - [PATCH] udf: fix dvd mounting error

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Date:   Thu, 15 Nov 2018 12:26:00 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Jan Kara <jack@...e.com>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>
Subject: [PATCH] udf: fix dvd mounting error

Some DVDs are failing to mount with the error:

[  632.305370] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[  632.305372] UDF-fs: Scanning with blocksize 512 failed
[  632.307837] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[  632.307839] UDF-fs: Scanning with blocksize 1024 failed
[  632.309320] UDF-fs: incorrect dstring lengths (32/32)
[  632.309361] UDF-fs: Scanning with blocksize 2048 failed
[  632.309530] UDF-fs: warning (device loop0): udf_load_vrs: No VRS found
[  632.309531] UDF-fs: Scanning with blocksize 4096 failed

This particular DVD used to work with v4.4 kernels, and has stopped
working after updating the kernel to v4.14. Did a git bisect and that
pointed to:
c26f6c615788 ("udf: Fix conversion of 'dstring' fields to UTF8")

This patch effectively reverts c26f6c615788 and removes the length
check that it introduced. And after this patch:

[   61.767204] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[   61.767206] UDF-fs: Scanning with blocksize 512 failed
[   61.770011] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[   61.770026] UDF-fs: Scanning with blocksize 1024 failed
[   61.773006] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[   61.773007] UDF-fs: Scanning with blocksize 512 failed
[   61.774401] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[   61.774402] UDF-fs: Scanning with blocksize 1024 failed
[   61.775045] UDF-fs: INFO Mounting volume 'TOUR_2017_THANKSGIVING_25_DISC ',
			timestamp 2018/01/30 05:57 (1000)

The DVD is available at:
https://www.amazon.co.jp/Live-%E3%80%8CMr-Children-DOME-STADIUM-Thanksgiving/dp/B079B5W6KC

Cc: Andrew Gabbasov <andrew_gabbasov@...tor.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
---

I dont't think this is the correct fix but has solved the problem for
now. I have the iso image of the DVD for testing, and if there is a better
solution I can test.

 fs/udf/unicode.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
index 45234791fec2..9f80c56178a5 100644
--- a/fs/udf/unicode.c
+++ b/fs/udf/unicode.c
@@ -356,14 +356,8 @@ int udf_dstrCS0toChar(struct super_block *sb, uint8_t *utf_o, int o_len,
 {
 	int s_len = 0;
 
-	if (i_len > 0) {
+	if (i_len > 0)
 		s_len = ocu_i[i_len - 1];
-		if (s_len >= i_len) {
-			pr_err("incorrect dstring lengths (%d/%d)\n",
-			       s_len, i_len);
-			return -EINVAL;
-		}
-	}
 
 	return udf_name_from_CS0(sb, utf_o, o_len, ocu_i, s_len, 0);
 }
-- 
2.11.0