git: 98727c6cd11e - main - Fix panic when using BOOTP to resolve root path.

[Brandon Bergren]

The branch main has been updated by bdragon:

URL: https://cgit.FreeBSD.org/src/commit/?id=98727c6cd11edb10617be0f421e485e0223185a5

commit 98727c6cd11edb10617be0f421e485e0223185a5
Author:     Brandon Bergren <bdragon at FreeBSD.org>
AuthorDate: 2021-03-28 00:18:51 +0000
Commit:     Brandon Bergren <bdragon at FreeBSD.org>
CommitDate: 2021-03-28 19:02:40 +0000

    Fix panic when using BOOTP to resolve root path.
    
    When loading a direct-boot kernel, a temporary route is being installed,
    the NFS handle is acquired, and the temporary route is removed again.
    
    This was being done inside a net epoch, but since the krpc code is written
    using blocking APIs, we can't actually do that, because sleeping is not
    allowed during a net epoch.
    
    Exit and reenter the epoch so we are only in the epoch when doing the
    routing table manipulation.
    
    Fixes panic when booting my RB800 over NFS (where the kernel is loaded
    using RouterBOOT directly.)
    
    Reviewed by:    melifaro
    Sponsored by:   Tag1 Consulting, Inc.
    Differential Revision:  https://reviews.freebsd.org/D29464
---
 sys/nfs/bootp_subr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/nfs/bootp_subr.c b/sys/nfs/bootp_subr.c
index fd0e0653a02c..2386a23084da 100644
--- a/sys/nfs/bootp_subr.c
+++ b/sys/nfs/bootp_subr.c
@@ -1682,9 +1682,11 @@ retry:
 
 		NET_EPOCH_ENTER(et);
 		bootpc_add_default_route(ifctx);
+		NET_EPOCH_EXIT(et);
 		error = md_mount(&nd->root_saddr, nd->root_hostnam,
 				 nd->root_fh, &nd->root_fhsize,
 				 &nd->root_args, td);
+		NET_EPOCH_ENTER(et);
 		bootpc_remove_default_route(ifctx);
 		NET_EPOCH_EXIT(et);
 		if (error != 0) {