From 01cdddde39b065074fd48f07027757783cbf5b7d Mon Sep 17 00:00:00 2001 From: =?utf8?q?Pali=20Roh=C3=A1r?= Date: Fri, 22 Nov 2024 16:29:43 +0100 Subject: [PATCH] cifs: Fix buffer overflow when parsing NFS reparse points MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit e2a8910af01653c1c268984855629d71fb81f404 upstream. 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) Signed-off-by: Pali Rohár Signed-off-by: Steve French [use variable name symlink_buf, the other buf->InodeType accesses are not used in current version so skip] Signed-off-by: Mahmoud Adam Signed-off-by: Sasha Levin --- fs/cifs/smb2ops.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 6c30fff8a029e..ee9a1e6550e3c 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -2971,6 +2971,12 @@ parse_reparse_posix(struct reparse_posix_data *symlink_buf, /* See MS-FSCC 2.1.2.6 for the 'NFS' style reparse tags */ len = le16_to_cpu(symlink_buf->ReparseDataLength); + if (len < sizeof(symlink_buf->InodeType)) { + cifs_dbg(VFS, "srv returned malformed nfs buffer\n"); + return -EIO; + } + + len -= sizeof(symlink_buf->InodeType); if (le64_to_cpu(symlink_buf->InodeType) != NFS_SPECFILE_LNK) { cifs_dbg(VFS, "%lld not a supported symlink type\n", -- 2.47.3