git: ed1acef3fe30 - stable/13 - ipfw: Update the pfil mbuf pointer in ipfw_check_frame()

[Mark Johnston]

The branch stable/13 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=ed1acef3fe3053b418ce3e41036ccf24957253a4

commit ed1acef3fe3053b418ce3e41036ccf24957253a4
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-06-16 13:46:56 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-06-19 14:08:49 +0000

    ipfw: Update the pfil mbuf pointer in ipfw_check_frame()
    
    ipfw_chk() might call m_pullup() and thus can change the mbuf chain
    head.  In this case, the new chain head has to be returned to the pfil
    hook caller, otherwise the pfil hook caller is left with a dangling
    pointer.
    
    Note that this affects only the link-layer hooks installed when the
    net.link.ether.ipfw sysctl is set to 1.
    
    PR:             256439, 254015, 255069, 255104
    Fixes:          f355cb3e6
    Reviewed by:    ae
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit bc6a2267fffeafd3946637607a74cfd639398f9d)
---
 sys/netpfil/ipfw/ip_fw_pfil.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/netpfil/ipfw/ip_fw_pfil.c b/sys/netpfil/ipfw/ip_fw_pfil.c
index e21831c80ec6..01a44df47180 100644
--- a/sys/netpfil/ipfw/ip_fw_pfil.c
+++ b/sys/netpfil/ipfw/ip_fw_pfil.c
@@ -371,6 +371,8 @@ again:
 	}
 
 	ipfw = ipfw_chk(&args);
+	if (!mem)
+		*p.m = args.m;
 
 	ret = PFIL_PASS;
 	switch (ipfw) {