netdev - [PATCH net] ipmr: do not call mr_mfc_uses

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Message-ID: <20250121181241.841212-1-edumazet@google.com>
Date: Tue, 21 Jan 2025 18:12:41 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Simon Horman <horms@...nel.org>, 
	David Ahern <dsahern@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, syzbot+5cfae50c0e5f2c500013@...kaller.appspotmail.com
Subject: [PATCH net] ipmr: do not call mr_mfc_uses_dev() for unres entries

syzbot found that calling mr_mfc_uses_dev() for unres entries
would crash [1], because c->mfc_un.res.minvif / c->mfc_un.res.maxvif
alias to "struct sk_buff_head unresolved", which contain two pointers.

This code never worked, lets remove it.

[1]
Unable to handle kernel paging request at virtual address ffff5fff2d536613
KASAN: maybe wild-memory-access in range [0xfffefff96a9b3098-0xfffefff96a9b309f]
Modules linked in:
CPU: 1 UID: 0 PID: 7321 Comm: syz.0.16 Not tainted 6.13.0-rc7-syzkaller-g1950a0af2d55 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : mr_mfc_uses_dev net/ipv4/ipmr_base.c:290 [inline]
 pc : mr_table_dump+0x5a4/0x8b0 net/ipv4/ipmr_base.c:334
 lr : mr_mfc_uses_dev net/ipv4/ipmr_base.c:289 [inline]
 lr : mr_table_dump+0x694/0x8b0 net/ipv4/ipmr_base.c:334
Call trace:
  mr_mfc_uses_dev net/ipv4/ipmr_base.c:290 [inline] (P)
  mr_table_dump+0x5a4/0x8b0 net/ipv4/ipmr_base.c:334 (P)
  mr_rtm_dumproute+0x254/0x454 net/ipv4/ipmr_base.c:382
  ipmr_rtm_dumproute+0x248/0x4b4 net/ipv4/ipmr.c:2648
  rtnl_dump_all+0x2e4/0x4e8 net/core/rtnetlink.c:4327
  rtnl_dumpit+0x98/0x1d0 net/core/rtnetlink.c:6791
  netlink_dump+0x4f0/0xbc0 net/netlink/af_netlink.c:2317
  netlink_recvmsg+0x56c/0xe64 net/netlink/af_netlink.c:1973
  sock_recvmsg_nosec net/socket.c:1033 [inline]
  sock_recvmsg net/socket.c:1055 [inline]
  sock_read_iter+0x2d8/0x40c net/socket.c:1125
  new_sync_read fs/read_write.c:484 [inline]
  vfs_read+0x740/0x970 fs/read_write.c:565
  ksys_read+0x15c/0x26c fs/read_write.c:708

Fixes: cb167893f41e ("net: Plumb support for filtering ipv4 and ipv6 multicast route dumps")
Reported-by: syzbot+5cfae50c0e5f2c500013@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/678fe2d1.050a0220.15cac.00b3.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/ipmr_base.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c
index f0af12a2f70bcdf5ba54321bf7ebebe798318ab..de98ce66d38f39fd77650f5143aab8f91ced2fc 100644
--- a/net/ipv4/ipmr_base.c
+++ b/net/ipv4/ipmr_base.c
@@ -330,9 +330,6 @@ int mr_table_dump(struct mr_table *mrt, struct sk_buff *skb,
 	list_for_each_entry(mfc, &mrt->mfc_unres_queue, list) {
 		if (e < s_e)
 			goto next_entry2;
-		if (filter->dev &&
-		    !mr_mfc_uses_dev(mrt, mfc, filter->dev))
-			goto next_entry2;
 
 		err = fill(mrt, skb, NETLINK_CB(cb->skb).portid,
 			   cb->nlh->nlmsg_seq, mfc, RTM_NEWROUTE, flags);
-- 
2.48.0.rc2.279.g1de40edade-goog