git: 8711fd2103d2 - stable/13 - kern_ntptime: Fix undefined behavior of the shift operator

The branch stable/13 has been updated by cy:

URL: https://cgit.FreeBSD.org/src/commit/?id=8711fd2103d2a580bd4671f3f1c7da0fc791e5db

commit 8711fd2103d2a580bd4671f3f1c7da0fc791e5db
Author:     Dmitriy Alexandrov <d06alexandrov@users.noreply.github.com>
AuthorDate: 2023-06-08 09:08:46 +0000
Commit:     Cy Schubert <cy@FreeBSD.org>
CommitDate: 2023-06-23 04:34:11 +0000

    kern_ntptime: Fix undefined behavior of the shift operator
    
    L_LINT macro is used with negative numbers [i.e.
    L_LINT(time_freq, -MAXFREQ)], it could cause undefined
    behavior. It should be similar to the L_RSHIFT(v, n) macro.
    
    MFC after:      2 weeks
    Reviewed by:    cy
    Pull Request:   https://github.com/freebsd/freebsd-src/pull/769
    Signed-off-by: Dmitriy Alexandrov <d06alexandrov@gmail.com>
    (cherry picked from commit af9ce4e9bb7d717279e02d46455e85ef6fb828f7)
---
 sys/kern/kern_ntptime.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_ntptime.c b/sys/kern/kern_ntptime.c
index a8418248abd7..7e0595c4b643 100644
--- a/sys/kern/kern_ntptime.c
+++ b/sys/kern/kern_ntptime.c
@@ -73,7 +73,13 @@ typedef int64_t l_fp;
 #define L_MPY(v, a)	((v) *= (a))
 #define L_CLR(v)	((v) = 0)
 #define L_ISNEG(v)	((v) < 0)
-#define L_LINT(v, a)	((v) = (int64_t)(a) << 32)
+#define L_LINT(v, a) \
+	do { \
+		if ((a) < 0) \
+			((v) = -((int64_t)(-(a)) << 32)); \
+		else \
+			((v) = (int64_t)(a) << 32); \
+	} while (0)
 #define L_GINT(v)	((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
 
 /*