Patch "cifs: Fix buffer overflow when parsing NFS reparse points" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    cifs: Fix buffer overflow when parsing NFS reparse points

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cifs-fix-buffer-overflow-when-parsing-nfs-reparse-po.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit af69d18055692a87a8e9d17198063b13bc282bb3
Author: Pali Rohár <pali@xxxxxxxxxx>
Date:   Sun Sep 29 12:22:40 2024 +0200

    cifs: Fix buffer overflow when parsing NFS reparse points
    
    [ Upstream commit e2a8910af01653c1c268984855629d71fb81f404 ]
    
    ReparseDataLength is sum of the InodeType size and DataBuffer size.
    So to get DataBuffer size it is needed to subtract InodeType's size from
    ReparseDataLength.
    
    Function cifs_strndup_from_utf16() is currentlly accessing buf->DataBuffer
    at position after the end of the buffer because it does not subtract
    InodeType size from the length. Fix this problem and correctly subtract
    variable len.
    
    Member InodeType is present only when reparse buffer is large enough. Check
    for ReparseDataLength before accessing InodeType to prevent another invalid
    memory access.
    
    Major and minor rdev values are present also only when reparse buffer is
    large enough. Check for reparse buffer size before calling reparse_mkdev().
    
    Fixes: d5ecebc4900d ("smb3: Allow query of symlinks stored as reparse points")
    Reviewed-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
    Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
    Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 48c27581ec511..cfa03c166de8c 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -320,9 +320,16 @@ static int parse_reparse_posix(struct reparse_posix_data *buf,
 	unsigned int len;
 	u64 type;
 
+	len = le16_to_cpu(buf->ReparseDataLength);
+	if (len < sizeof(buf->InodeType)) {
+		cifs_dbg(VFS, "srv returned malformed nfs buffer\n");
+		return -EIO;
+	}
+
+	len -= sizeof(buf->InodeType);
+
 	switch ((type = le64_to_cpu(buf->InodeType))) {
 	case NFS_SPECFILE_LNK:
-		len = le16_to_cpu(buf->ReparseDataLength);
 		data->symlink_target = cifs_strndup_from_utf16(buf->DataBuffer,
 							       len, true,
 							       cifs_sb->local_nls);
@@ -482,12 +489,18 @@ bool cifs_reparse_point_to_fattr(struct cifs_sb_info *cifs_sb,
 	u32 tag = data->reparse.tag;
 
 	if (tag == IO_REPARSE_TAG_NFS && buf) {
+		if (le16_to_cpu(buf->ReparseDataLength) < sizeof(buf->InodeType))
+			return false;
 		switch (le64_to_cpu(buf->InodeType)) {
 		case NFS_SPECFILE_CHR:
+			if (le16_to_cpu(buf->ReparseDataLength) != sizeof(buf->InodeType) + 8)
+				return false;
 			fattr->cf_mode |= S_IFCHR;
 			fattr->cf_rdev = reparse_nfs_mkdev(buf);
 			break;
 		case NFS_SPECFILE_BLK:
+			if (le16_to_cpu(buf->ReparseDataLength) != sizeof(buf->InodeType) + 8)
+				return false;
 			fattr->cf_mode |= S_IFBLK;
 			fattr->cf_rdev = reparse_nfs_mkdev(buf);
 			break;