Re: [PATCH 4.9 41/51] fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied

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On Sun, May 19, 2019 at 08:43:48AM -0700, Nathan Chancellor wrote:
On Wed, May 15, 2019 at 12:56:16PM +0200, Greg Kroah-Hartman wrote:
From: Hangbin Liu <liuhangbin@xxxxxxxxx>

[ Upstream commit e9919a24d3022f72bcadc407e73a6ef17093a849 ]

With commit 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to
fib_nl_newrule") we now able to check if a rule already exists. But this
only works with iproute2. For other tools like libnl, NetworkManager,
it still could add duplicate rules with only NLM_F_CREATE flag, like

[localhost ~ ]# ip rule
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default
100000: from 192.168.7.5 lookup 5
100000: from 192.168.7.5 lookup 5

As it doesn't make sense to create two duplicate rules, let's just return
0 if the rule exists.

Fixes: 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to fib_nl_newrule")
Reported-by: Thomas Haller <thaller@xxxxxxxxxx>
Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/fib_rules.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -429,9 +429,9 @@ int fib_nl_newrule(struct sk_buff *skb,
 	if (rule->l3mdev && rule->table)
 		goto errout_free;

-	if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
-	    rule_exists(ops, frh, tb, rule)) {
-		err = -EEXIST;
+	if (rule_exists(ops, frh, tb, rule)) {
+		if (nlh->nlmsg_flags & NLM_F_EXCL)
+			err = -EEXIST;
 		goto errout_free;
 	}




Hi all,

This commit is causing issues on Android devices when Wi-Fi and mobile
data are both enabled. The device will do a soft reboot consistently.
So far, I've had reports on the Pixel 3 XL, OnePlus 6, Pocophone, and
Note 9 and I can reproduce on my OnePlus 6.

Is this something that happens with Linus's tree as well? or is this a
backport issue?

Sorry for taking so long to report this, I just figured out how to
reproduce it today and I didn't want to report it without that.

FWIW, if you see anything suspicious with -stable patches just let us
know separately from a "better" bug report for upstream, then we can at
least temporary pull it out of the stable queue while the issue is being
addressed.

--
Thanks,
Sasha



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