diff mbox series

cifs: Fix buffer overflow when parsing NFS reparse points

Message ID 20241122134410.124563-1-mngyadam@amazon.com (mailing list archive)
State New
Headers show
Series cifs: Fix buffer overflow when parsing NFS reparse points | expand

Commit Message

Mahmoud Adam Nov. 22, 2024, 1:44 p.m. UTC 
From: Pali Rohár <pali@kernel.org>

upstream e2a8910af01653c1c268984855629d71fb81f404 commit.

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@manguebit.com>
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
[use variable name symlink_buf, the other buf->InodeType accesses are
not used in current version so skip]
Signed-off-by: Mahmoud Adam <mngyadam@amazon.com>
---
This fixes CVE-2024-49996, and applies cleanly on 5.4->6.1, 6.6 and
later already has the fix.
 fs/smb/client/smb2ops.c | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index d1e5ff9a3cd39..fcfbc096924a8 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2897,6 +2897,12 @@  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",