Patch "rtnetlink: add RTNL_FLAG_DUMP_UNLOCKED flag" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    rtnetlink: add RTNL_FLAG_DUMP_UNLOCKED flag

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rtnetlink-add-rtnl_flag_dump_unlocked-flag.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 63325c4b7845dd88cdf0f8d577ca1984f711fe28
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu Feb 22 10:50:15 2024 +0000

    rtnetlink: add RTNL_FLAG_DUMP_UNLOCKED flag
    
    [ Upstream commit 386520e0ecc01004d3a29c70c5a77d4bbf8a8420 ]
    
    Similarly to RTNL_FLAG_DOIT_UNLOCKED, this new flag
    allows dump operations registered via rtnl_register()
    or rtnl_register_module() to opt-out from RTNL protection.
    
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reviewed-by: Donald Hunter <donald.hunter@xxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Stable-dep-of: 5be2062e3080 ("mpls: Handle error of rtnl_register_module().")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 75d7de34c9087..e8d713a37d176 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -289,6 +289,7 @@ struct netlink_callback {
 	u16			answer_flags;
 	u32			min_dump_alloc;
 	unsigned int		prev_seq, seq;
+	int			flags;
 	bool			strict_check;
 	union {
 		u8		ctx[48];
@@ -321,6 +322,7 @@ struct netlink_dump_control {
 	void *data;
 	struct module *module;
 	u32 min_dump_alloc;
+	int flags;
 };
 
 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index 0bd400be3f8d9..c1fa6fee0acfa 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -12,6 +12,7 @@ typedef int (*rtnl_dumpit_func)(struct sk_buff *, struct netlink_callback *);
 enum rtnl_link_flags {
 	RTNL_FLAG_DOIT_UNLOCKED		= BIT(0),
 	RTNL_FLAG_BULK_DEL_SUPPORTED	= BIT(1),
+	RTNL_FLAG_DUMP_UNLOCKED		= BIT(2),
 };
 
 enum rtnl_kinds {
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index ffa1334cddf44..c76c54879fddd 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -6405,6 +6405,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 		}
 		owner = link->owner;
 		dumpit = link->dumpit;
+		flags = link->flags;
 
 		if (type == RTM_GETLINK - RTM_BASE)
 			min_dump_alloc = rtnl_calcit(skb, nlh);
@@ -6422,6 +6423,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 				.dump		= dumpit,
 				.min_dump_alloc	= min_dump_alloc,
 				.module		= owner,
+				.flags		= flags,
 			};
 			err = netlink_dump_start(rtnl, skb, nlh, &c);
 			/* netlink_dump_start() will keep a reference on
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e40376997f393..8e7d5f17c58b8 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2263,6 +2263,8 @@ static int netlink_dump(struct sock *sk, bool lock_taken)
 
 		cb->extack = &extack;
 
+		if (cb->flags & RTNL_FLAG_DUMP_UNLOCKED)
+			extra_mutex = NULL;
 		if (extra_mutex)
 			mutex_lock(extra_mutex);
 		nlk->dump_done_errno = cb->dump(skb, cb);
@@ -2357,6 +2359,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 	cb->data = control->data;
 	cb->module = control->module;
 	cb->min_dump_alloc = control->min_dump_alloc;
+	cb->flags = control->flags;
 	cb->skb = skb;
 
 	cb->strict_check = nlk_test_bit(STRICT_CHK, NETLINK_CB(skb).sk);