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. 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",