CVE-2014-9731 (published 2015-08-31T10:59Z)

The UDF filesystem implementation in the Linux kernel before 3.18.2 does not ensure that space is available for storing a symlink target's name along with a trailing \\0 character, which allows local users to obtain sensitive information via a crafted filesystem image, related to fs/udf/symlink.c and fs/udf/unicode.c.

Severity: LOW
CVSS v2 base score: 2.1 (AV:L/AC:L/Au:N/C:P/I:N/A:N)

Weakness information:
cwe_id: CWE-17
cwe_name: DEPRECATED: Code
description: This entry has been deprecated.  It was originally used for organizing the Development View (CWE-699) and some other views, but it introduced unnecessary complexity and depth to the resulting tree.

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Jan Kara
author_date: 2014-12-18 22:37:50+01:00
msg: udf: Check path length when reading symlink

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.

CC: stable@vger.kernel.org
Reported-by: Carl Henrik Lunde <chlunde@ping.uio.no>
Signed-off-by: Jan Kara <jack@suse.cz>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: dir.c
change_type: ModificationType.MODIFY
diff: @@ -167,7 +167,8 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
 			continue;
 		}
 
-		flen = udf_get_filename(dir->i_sb, nameptr, fname, lfi);
+		flen = udf_get_filename(dir->i_sb, nameptr, lfi, fname,
+					UDF_NAME_LEN);
 		if (!flen)
 			continue;
 

programming_language: C
filename: namei.c
change_type: ModificationType.MODIFY
diff: @@ -233,7 +233,8 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 		if (!lfi)
 			continue;
 
-		flen = udf_get_filename(dir->i_sb, nameptr, fname, lfi);
+		flen = udf_get_filename(dir->i_sb, nameptr, lfi, fname,
+					UDF_NAME_LEN);
 		if (flen && udf_match(flen, fname, child->len, child->name))
 			goto out_ok;
 	}

programming_language: C
filename: symlink.c
change_type: ModificationType.MODIFY
diff: @@ -30,13 +30,16 @@
 #include <linux/buffer_head.h>
 #include "udf_i.h"
 
-static void udf_pc_to_char(struct super_block *sb, unsigned char *from,
-			   int fromlen, unsigned char *to)
+static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
+			  int fromlen, unsigned char *to, int tolen)
 {
 	struct pathComponent *pc;
 	int elen = 0;
+	int comp_len;
 	unsigned char *p = to;
 
+	/* Reserve one byte for terminating \0 */
+	tolen--;
 	while (elen < fromlen) {
 		pc = (struct pathComponent *)(from + elen);
 		switch (pc->componentType) {
@@ -49,22 +52,37 @@ static void udf_pc_to_char(struct super_block *sb, unsigned char *from,
 				break;
 			/* Fall through */
 		case 2:
+			if (tolen == 0)
+				return -ENAMETOOLONG;
 			p = to;
 			*p++ = '/';
+			tolen--;
 			break;
 		case 3:
+			if (tolen < 3)
+				return -ENAMETOOLONG;
 			memcpy(p, "../", 3);
 			p += 3;
+			tolen -= 3;
 			break;
 		case 4:
+			if (tolen < 2)
+				return -ENAMETOOLONG;
 			memcpy(p, "./", 2);
 			p += 2;
+			tolen -= 2;
 			/* that would be . - just ignore */
 			break;
 		case 5:
-			p += udf_get_filename(sb, pc->componentIdent, p,
-					      pc->lengthComponentIdent);
+			comp_len = udf_get_filename(sb, pc->componentIdent,
+						    pc->lengthComponentIdent,
+						    p, tolen);
+			p += comp_len;
+			tolen -= comp_len;
+			if (tolen == 0)
+				return -ENAMETOOLONG;
 			*p++ = '/';
+			tolen--;
 			break;
 		}
 		elen += sizeof(struct pathComponent) + pc->lengthComponentIdent;
@@ -73,6 +91,7 @@ static void udf_pc_to_char(struct super_block *sb, unsigned char *from,
 		p[-1] = '\0';
 	else
 		p[0] = '\0';
+	return 0;
 }
 
 static int udf_symlink_filler(struct file *file, struct page *page)
@@ -108,8 +127,10 @@ static int udf_symlink_filler(struct file *file, struct page *page)
 		symlink = bh->b_data;
 	}
 
-	udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
+	err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
 	brelse(bh);
+	if (err)
+		goto out_unlock_inode;
 
 	up_read(&iinfo->i_data_sem);
 	SetPageUptodate(page);

programming_language: C
filename: udfdecl.h
change_type: ModificationType.MODIFY
diff: @@ -211,7 +211,8 @@ udf_get_lb_pblock(struct super_block *sb, struct kernel_lb_addr *loc,
 }
 
 /* unicode.c */
-extern int udf_get_filename(struct super_block *, uint8_t *, uint8_t *, int);
+extern int udf_get_filename(struct super_block *, uint8_t *, int, uint8_t *,
+			    int);
 extern int udf_put_filename(struct super_block *, const uint8_t *, uint8_t *,
 			    int);
 extern int udf_build_ustr(struct ustr *, dstring *, int);

programming_language: C
filename: unicode.c
change_type: ModificationType.MODIFY
diff: @@ -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 @@ static int udf_NLStoCS0(struct nls_table *nls, dstring *ocu, struct ustr *uni,
 	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;
@@ -439,7 +443,7 @@ 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;
@@ -467,13 +471,13 @@ 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++] = hex_asc_upper_hi(valueCRC >> 8);

programming_language: C