From 1101d628223d2188c244a4df9b0cb4eaff57e968 Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Mon, 7 Apr 2025 14:03:50 +0000
Subject: [PATCH] copy_file_range: Fix overlap checking

The check for range overlap did not correctly handle negative offests,
as the addition inoff + len is promoted to an unsigned type.

Reported by:	syzkaller
Reviewed by:	rmacklem
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D49674
---
 sys/kern/vfs_syscalls.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 1a3400a87ee..7b71ffc7689 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -5075,6 +5075,15 @@ kern_copy_file_range(struct thread *td, int infd, off_t *inoffp, int outfd,
 	if (len == 0)
 		goto out;
 
+	/*
+	 * Make sure that the ranges we check and lock below are valid.  Note
+	 * that len is clamped to SSIZE_MAX above.
+	 */
+	if (inoff < 0 || outoff < 0) {
+		error = EINVAL;
+		goto out;
+	}
+
 	/*
 	 * If infp and outfp refer to the same file, the byte ranges cannot
 	 * overlap.