From 399aa12450a61a5c73dc77e73f069ece9687c95d Mon Sep 17 00:00:00 2001 From: Aleksandr Khromov Date: Mon, 24 Aug 2026 13:22:46 +0300 Subject: [PATCH] ksmbd: zero the FS_OBJECT_ID_INFORMATION buffer before filling it in smb2_get_info_filesystem() reports 64 bytes for FS_OBJECT_ID_INFORMATION, that is the whole of struct object_id_info, but writes only 46 of them: - objid[] is 16 bytes, and when the volume UUID is not available only sizeof(stfs.f_fsid) (8) bytes are copied into it; - extended_info.version_string[] is STRING_LENGTH (28) bytes, and only strlen("1.1.0") (5) bytes are copied into it. The response buffer is zeroed on allocation (kvzalloc() in smb2_allocate_rsp_buf()), so for a standalone request the remaining 31 bytes are zero. In a compound request they need not be. The offset of the next response is advanced by the length pinned for the previous one, so if a preceding command wrote its reply into the buffer and then failed, smb2_set_err_rsp() pins only the short error response and the next reply lands inside the area that has already been written. Only the header is cleared there: memset((char *)rsp_hdr, 0, sizeof(struct smb2_hdr) + 2); The client then receives up to 31 bytes of a response it was not meant to see, including one that failed with an access denied error. Clear the structure before filling it in. As a side effect version_string is now NUL terminated. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Suggested-by: ChenXiaoSong Cc: stable@vger.kernel.org Signed-off-by: Aleksandr Khromov Signed-off-by: Namjae Jeon --- fs/smb/server/smb2pdu.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index a8046f477d54..486cd745dd21 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -7444,6 +7444,7 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work, struct object_id_info *info; info = (struct object_id_info *)(rsp->Buffer); + memset(info, 0, sizeof(*info)); if (path.mnt->mnt_sb->s_uuid_len == 16) memcpy(info->objid, path.mnt->mnt_sb->s_uuid.b,