request for 4.14-stable: b54e41f5efcb ("udf: Allow mounting volumes with incorrect identification strings")

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

This has been applied to 4.19-stable, but should be needed in
4.14-stable also. I have attached the backported patch and have
also tested with one such DVD where the problem was seen.


--
Regards
Sudip

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>From 197a1e1728bb1aab5a2e747a04ecd90390b1d8b7 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Fri, 16 Nov 2018 13:43:17 +0100
Subject: [PATCH] udf: Allow mounting volumes with incorrect identification strings

commit b54e41f5efcb4316b2f30b30c2535cc194270373 upstream.

Commit c26f6c615788 ("udf: Fix conversion of 'dstring' fields to UTF8")
started to be more strict when checking whether converted strings are
properly formatted. Sudip reports that there are DVDs where the volume
identification string is actually too long - UDF reports:

[  632.309320] UDF-fs: incorrect dstring lengths (32/32)

during mount and fails the mount. This is mostly harmless failure as we
don't need volume identification (and even less volume set
identification) for anything. So just truncate the volume identification
string if it is too long and replace it with 'Invalid' if we just cannot
convert it for other reasons. This keeps slightly incorrect media still
mountable.

CC: stable@vger.kernel.org
Fixes: c26f6c615788 ("udf: Fix conversion of 'dstring' fields to UTF8")
Reported-and-tested-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 fs/udf/super.c   | 16 ++++++++++------
 fs/udf/unicode.c | 14 +++++++++++---
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 9b0d6562d0a1..242d960df9a1 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -922,16 +922,20 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
 	}
 
 	ret = udf_dstrCS0toUTF8(outstr, 31, pvoldesc->volIdent, 32);
-	if (ret < 0)
-		goto out_bh;
-
-	strncpy(UDF_SB(sb)->s_volume_ident, outstr, ret);
+	if (ret < 0) {
+		strcpy(UDF_SB(sb)->s_volume_ident, "InvalidName");
+		pr_warn("incorrect volume identification, setting to "
+			"'InvalidName'\n");
+	} else {
+		strncpy(UDF_SB(sb)->s_volume_ident, outstr, ret);
+	}
 	udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);
 
 	ret = udf_dstrCS0toUTF8(outstr, 127, pvoldesc->volSetIdent, 128);
-	if (ret < 0)
+	if (ret < 0) {
+		ret = 0;
 		goto out_bh;
-
+	}
 	outstr[ret] = 0;
 	udf_debug("volSetIdent[] = '%s'\n", outstr);
 
diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
index 3a3be23689b3..61a1738895b7 100644
--- a/fs/udf/unicode.c
+++ b/fs/udf/unicode.c
@@ -341,6 +341,11 @@ static int udf_name_to_CS0(uint8_t *ocu, int ocu_max_len,
 	return u_len;
 }
 
+/*
+ * Convert CS0 dstring to output charset. Warning: This function may truncate
+ * input string if it is too long as it is used for informational strings only
+ * and it is better to truncate the string than to refuse mounting a media.
+ */
 int udf_dstrCS0toUTF8(uint8_t *utf_o, int o_len,
 		      const uint8_t *ocu_i, int i_len)
 {
@@ -349,9 +354,12 @@ int udf_dstrCS0toUTF8(uint8_t *utf_o, int o_len,
 	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;
+			pr_warn("incorrect dstring lengths (%d/%d),"
+				" truncating\n", s_len, i_len);
+			s_len = i_len - 1;
+			/* 2-byte encoding? Need to round properly... */
+			if (ocu_i[0] == 16)
+				s_len -= (s_len - 1) & 2;
 		}
 	}
 
-- 
2.11.0