udf: Check path length when reading symlink

commit 0e5cc9a40ada6046e6bc3bdfcd0c0d7e4b706b14 upstream.

Symlink reading code does not check whether the resulting path fits into
the page provided by the generic code. This isn't as easy as just
checking the symlink size because of various encoding conversions we
perform on path. So we have to check whether there is still enough space
in the buffer on the fly.

Reported-by: Carl Henrik Lunde <chlunde@ping.uio.no>
Signed-off-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 16 insertions, 12 deletions

diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
index 44b815e..d29c06f 100644
--- a/fs/udf/unicode.c
+++ b/fs/udf/unicode.c
@@ -28,7 +28,8 @@
 
 #include "udf_sb.h"
 
-static int udf_translate_to_linux(uint8_t *, uint8_t *, int, uint8_t *, int);
+static int udf_translate_to_linux(uint8_t *, int, uint8_t *, int, uint8_t *,
+				  int);
 
 static int udf_char_to_ustr(struct ustr *dest, const uint8_t *src, int strlen)
 {
@@ -333,8 +334,8 @@ try_again:
 	return u_len + 1;
 }
 
-int udf_get_filename(struct super_block *sb, uint8_t *sname, uint8_t *dname,
-		     int flen)
+int udf_get_filename(struct super_block *sb, uint8_t *sname, int slen,
+		     uint8_t *dname, int dlen)
 {
 	struct ustr *filename, *unifilename;
 	int len = 0;
@@ -347,7 +348,7 @@ int udf_get_filename(struct super_block *sb, uint8_t *sname, uint8_t *dname,
 	if (!unifilename)
 		goto out1;
 
-	if (udf_build_ustr_exact(unifilename, sname, flen))
+	if (udf_build_ustr_exact(unifilename, sname, slen))
 		goto out2;
 
 	if (UDF_QUERY_FLAG(sb, UDF_FLAG_UTF8)) {
@@ -366,7 +367,8 @@ int udf_get_filename(struct super_block *sb, uint8_t *sname, uint8_t *dname,
 	} else
 		goto out2;
 
-	len = udf_translate_to_linux(dname, filename->u_name, filename->u_len,
+	len = udf_translate_to_linux(dname, dlen,
+				     filename->u_name, filename->u_len,
 				     unifilename->u_name, unifilename->u_len);
 out2:
 	kfree(unifilename);
@@ -403,10 +405,12 @@ int udf_put_filename(struct super_block *sb, const uint8_t *sname,
 #define EXT_MARK		'.'
 #define CRC_MARK		'#'
 #define EXT_SIZE 		5
+/* Number of chars we need to store generated CRC to make filename unique */
+#define CRC_LEN			5
 
-static int udf_translate_to_linux(uint8_t *newName, uint8_t *udfName,
-				  int udfLen, uint8_t *fidName,
-				  int fidNameLen)
+static int udf_translate_to_linux(uint8_t *newName, int newLen,
+				  uint8_t *udfName, int udfLen,
+				  uint8_t *fidName, int fidNameLen)
 {
 	int index, newIndex = 0, needsCRC = 0;
 	int extIndex = 0, newExtIndex = 0, hasExt = 0;
@@ -440,7 +444,7 @@ static int udf_translate_to_linux(uint8_t *newName, uint8_t *udfName,
 					newExtIndex = newIndex;
 				}
 			}
-			if (newIndex < 256)
+			if (newIndex < newLen)
 				newName[newIndex++] = curr;
 			else
 				needsCRC = 1;
@@ -468,13 +472,13 @@ static int udf_translate_to_linux(uint8_t *newName, uint8_t *udfName,
 				}
 				ext[localExtIndex++] = curr;
 			}
-			maxFilenameLen = 250 - localExtIndex;
+			maxFilenameLen = newLen - CRC_LEN - localExtIndex;
 			if (newIndex > maxFilenameLen)
 				newIndex = maxFilenameLen;
 			else
 				newIndex = newExtIndex;
-		} else if (newIndex > 250)
-			newIndex = 250;
+		} else if (newIndex > newLen - CRC_LEN)
+			newIndex = newLen - CRC_LEN;
 		newName[newIndex++] = CRC_MARK;
 		valueCRC = crc_itu_t(0, fidName, fidNameLen);
 		newName[newIndex++] = hexChar[(valueCRC & 0xf000) >> 12];