git: 98e1ee23857c - stable/13 - kern: zero out stack buffer after copying out random bits

The branch stable/13 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=98e1ee23857cf858a66dff23b39f80ede00d2311

commit 98e1ee23857cf858a66dff23b39f80ede00d2311
Author:     Kyle Evans <kevans@FreeBSD.org>
AuthorDate: 2024-07-15 20:17:47 +0000
Commit:     Kyle Evans <kevans@FreeBSD.org>
CommitDate: 2024-07-21 05:25:12 +0000

    kern: zero out stack buffer after copying out random bits
    
    The kern.arandom sysctl handler uses an intermediate buffer on the stack
    to hold random data that it subsequently copies out to the sysctl
    request.  Err on the side of caution and zero out the stack buffer after
    we're done with it to avoid a potential entropy leak later on.
    
    Reviewed by:    cem, emaste, markj
    
    (cherry picked from commit 5862c891bb7c588aa00538d85eb26ffe77d3f709)
---
 sys/kern/kern_mib.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_mib.c b/sys/kern/kern_mib.c
index c9056503925f..aa4798a5a956 100644
--- a/sys/kern/kern_mib.c
+++ b/sys/kern/kern_mib.c
@@ -182,10 +182,14 @@ sysctl_kern_arnd(SYSCTL_HANDLER_ARGS)
 {
 	char buf[256];
 	size_t len;
+	int error;
 
 	len = MIN(req->oldlen, sizeof(buf));
 	read_random(buf, len);
-	return (SYSCTL_OUT(req, buf, len));
+
+	error = SYSCTL_OUT(req, buf, len);
+	explicit_bzero(buf, len);
+	return (error);
 }
 
 SYSCTL_PROC(_kern, KERN_ARND, arandom,