git: 827dccf3ff5c - stable/15 - linuxkpi: Fix an off-by-one error in the kfifo implementation

The branch stable/15 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=827dccf3ff5c48b2f62378a44f58bf287fe99550

commit 827dccf3ff5c48b2f62378a44f58bf287fe99550
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2026-04-15 13:33:04 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2026-04-22 12:37:07 +0000

    linuxkpi: Fix an off-by-one error in the kfifo implementation
    
    "total" is the number of slots in the array, so wraparound needs to be
    done when "first" or "last" is greater than or equal to the number of
    slots.
    
    Note that no consumers of the code are currently connected to the kernel
    build.
    
    Reported by:    Stanislav Fort <stanislav.fort@aisle.com>
    Reviewed by:    bz, emaste
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D56371
    
    (cherry picked from commit 52d2fc702b85d56b35f8828fe7efca3cde0d25b7)
---
 sys/compat/linuxkpi/common/include/linux/kfifo.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/compat/linuxkpi/common/include/linux/kfifo.h b/sys/compat/linuxkpi/common/include/linux/kfifo.h
index d2f570781661..b9f6ecacd3d1 100644
--- a/sys/compat/linuxkpi/common/include/linux/kfifo.h
+++ b/sys/compat/linuxkpi/common/include/linux/kfifo.h
@@ -71,7 +71,7 @@
 		(_kf)->head[(_kf)->last] = (_e);			\
 		(_kf)->count++;						\
 		(_kf)->last++;						\
-		if ((_kf)->last > (_kf)->total)				\
+		if ((_kf)->last >= (_kf)->total)			\
 			(_kf)->last = 0;				\
 		_rc = true;						\
 	}								\
@@ -89,7 +89,7 @@
 		*(_e) = (_kf)->head[(_kf)->first];			\
 		(_kf)->count--;						\
 		(_kf)->first++;						\
-		if ((_kf)->first > (_kf)->total)			\
+		if ((_kf)->first >= (_kf)->total)			\
 			(_kf)->first = 0;				\
 		_rc = true;						\
 	}								\