git: a2f57656620d - stable/13 - kern linker: Do not unload a module if it has dependants

The branch stable/13 has been updated by zlei:

URL: https://cgit.FreeBSD.org/src/commit/?id=a2f57656620d2ffbb8b79789de34a6fc657286d5

commit a2f57656620d2ffbb8b79789de34a6fc657286d5
Author:     Zhenlei Huang <zlei@FreeBSD.org>
AuthorDate: 2024-03-26 03:55:45 +0000
Commit:     Zhenlei Huang <zlei@FreeBSD.org>
CommitDate: 2024-04-09 04:13:08 +0000

    kern linker: Do not unload a module if it has dependants
    
    Despite the name, linker_file_unload() will drop a reference and return
    success when the module file has dependants, i.e. it has more than one
    reference. When user request to unload such modules then the kernel
    should reject unambiguously and immediately.
    
    PR:             274986
    Reviewed by:    dfr, dab, jhb
    MFC after:      2 weeks
    Differential Revision:  https://reviews.freebsd.org/D42527
    
    (cherry picked from commit f43ff3e15c8b4b161ce09c8ab008abc4222db26b)
    (cherry picked from commit f1994d1eb215a2b7cb644329797dc623ec883120)
---
 sys/kern/kern_linker.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/kern/kern_linker.c b/sys/kern/kern_linker.c
index bc2f477997e0..8f83fc4c474f 100644
--- a/sys/kern/kern_linker.c
+++ b/sys/kern/kern_linker.c
@@ -1207,6 +1207,8 @@ kern_kldunload(struct thread *td, int fileid, int flags)
 			printf("kldunload: attempt to unload file that was"
 			    " loaded by the kernel\n");
 			error = EBUSY;
+		} else if (lf->refs > 1) {
+			error = EBUSY;
 		} else {
 			lf->userrefs--;
 			error = linker_file_unload(lf, flags);