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New: POLLIN bit is set when there is OOB data only

Bugme-new Andrew Morton 2 participants 2 messages Mar 19, 2010 – Mar 20, 2010 1 message not in the archive

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Andrew Morton

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#1 lore raw
In reply to a message not in the archive

(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface).

Quoted 34 lines · On Mon, 15 Mar 2010 16:19:43 GMT [email protected] wrote:

http://bugzilla.kernel.org/show_bug.cgi?id=15541

           Summary: POLLIN bit is set when there is OOB data only
           Product: Networking
           Version: 2.5
    Kernel Version: 2.6.28, 2.6.32, 2.6.33
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV4
        AssignedTo: [email protected]
        ReportedBy: [email protected]
                CC: [email protected]
        Regression: Yes

Starting from 2.6.28, Linux kernel has incorrect behaviour when poll() is called on TCP socket with out-of-band byte received.

When TCP socket has OOB byte available (and no normal data), old Linux, Solaris, FreeBSD and other systems return POLLPRI bit without POLLRD. Starting from 2.6.28, Linux returns POLLRD | POLLPRI | POLLRDNORM.

The broken commt is
http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.28.y.git;a=commitdiff;h=c7004482e8dcb7c3c72666395cfa98a216a4fb70
.
Following 1-line patch fixes the problem:

net/ipv4/tcp.c 2010-03-15 19:13:21.000000000 +0300 line 434

Quoted 8 lines
net/ipv4/tcp.c 2010-03-15 19:13:21.000000000 +0300 renamed from net/ipv4/tcp.c 2010-03-15 19:13:45.000000000 +0300 +1 -1
@@ -428,7 +428,7 @@
                if (tp->urg_seq == tp->copied_seq &&
                    !sock_flag(sk, SOCK_URGINLINE) &&
                    tp->urg_data)
-                       target--;
+                       target++;
 
                /* Potential race condition. If read of tp below will
                 * escape above sk->sk_state, we can be illegally awaken

Thanks.

(Please don't send patches via bugzilla - it causes lots of problems with our usual patch management and review processes.

Please send this patch via email as per Documentation/SubmittingPatches. Suitable recipients may be found via scripts/get_maintainer.pl)

maintainer
#2 lore raw

The patch is already in Linus's tree Andrew.

Stephen Hemminger forwarded this bugzilla entry to netdev an I applied the patch a few days ago.