kernel/git/stable/linux.git/include/net/tcp.h, branch linux-3.2.y

tcp: fix tcp_mtu_probe() vs highest_sack

2018-01-01T20:51:00+00:00

commit 2b7cda9c35d3b940eb9ce74b30bbd5eb30db493d upstream. Based on SNMP values provided by Roman, Yuchung made the observation that some crashes in tcp_sacktag_walk() might be caused by MTU probing. Looking at tcp_mtu_probe(), I found that when a new skb was placed in front of the write queue, we were not updating tcp highest sack. If one skb is freed because all its content was copied to the new skb (for MTU probing), then tp->highest_sack could point to a now freed skb. Bad things would then happen, including infinite loops. This patch renames tcp_highest_sack_combine() and uses it from tcp_mtu_probe() to fix the bug. Note that I also removed one test against tp->sacked_out, since we want to replace tp->highest_sack regardless of whatever condition, since keeping a stale pointer to freed skb is a recipe for disaster. Fixes: a47e5a988a57 ("[TCP]: Convert highest_sack to sk_buff to allow direct access") Signed-off-by: Eric Dumazet Reported-by: Alexei Starovoitov Reported-by: Roman Gushchin Reported-by: Oleksandr Natalenko Acked-by: Alexei Starovoitov Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

tcp: take care of truncations done by sk_filter()

2017-02-23T03:51:05+00:00

commit ac6e780070e30e4c35bd395acfe9191e6268bdd3 upstream. With syzkaller help, Marco Grassi found a bug in TCP stack, crashing in tcp_collapse() Root cause is that sk_filter() can truncate the incoming skb, but TCP stack was not really expecting this to happen. It probably was expecting a simple DROP or ACCEPT behavior. We first need to make sure no part of TCP header could be removed. Then we need to adjust TCP_SKB_CB(skb)->end_seq Many thanks to syzkaller team and Marco for giving us a reproducer. Signed-off-by: Eric Dumazet Reported-by: Marco Grassi Reported-by: Vladis Dronov Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

tcp: fix use after free in tcp_xmit_retransmit_queue()

2016-11-20T01:01:33+00:00

commit bb1fceca22492109be12640d49f5ea5a544c6bb4 upstream. When tcp_sendmsg() allocates a fresh and empty skb, it puts it at the tail of the write queue using tcp_add_write_queue_tail() Then it attempts to copy user data into this fresh skb. If the copy fails, we undo the work and remove the fresh skb. Unfortunately, this undo lacks the change done to tp->highest_sack and we can leave a dangling pointer (to a freed skb) Later, tcp_xmit_retransmit_queue() can dereference this pointer and access freed memory. For regular kernels where memory is not unmapped, this might cause SACK bugs because tcp_highest_sack_seq() is buggy, returning garbage instead of tp->snd_nxt, but with various debug features like CONFIG_DEBUG_PAGEALLOC, this can crash the kernel. This bug was found by Marco Grassi thanks to syzkaller. Fixes: 6859d49475d4 ("[TCP]: Abstract tp->highest_sack accessing & point to next skb") Reported-by: Marco Grassi Signed-off-by: Eric Dumazet Cc: Ilpo Järvinen Cc: Yuchung Cheng Cc: Neal Cardwell Acked-by: Neal Cardwell Reviewed-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

tcp: md5: remove spinlock usage in fast path

2015-01-01T01:27:52+00:00

commit 71cea17ed39fdf1c0634f530ddc6a2c2fc601c2b upstream. TCP md5 code uses per cpu variables but protects access to them with a shared spinlock, which is a contention point. [ tcp_md5sig_pool_lock is locked twice per incoming packet ] Makes things much simpler, by allocating crypto structures once, first time a socket needs md5 keys, and not deallocating them as they are really small. Next step would be to allow crypto allocations being done in a NUMA aware way. Signed-off-by: Eric Dumazet Cc: Herbert Xu Signed-off-by: David S. Miller [bwh: Backported to 3.2: - Adjust context - Conditions for alloc/free are quite different] Signed-off-by: Ben Hutchings

tcp: be more strict before accepting ECN negociation

2014-12-14T16:24:00+00:00

commit bd14b1b2e29bd6812597f896dde06eaf7c6d2f24 upstream. It appears some networks play bad games with the two bits reserved for ECN. This can trigger false congestion notifications and very slow transferts. Since RFC 3168 (6.1.1) forbids SYN packets to carry CT bits, we can disable TCP ECN negociation if it happens we receive mangled CT bits in the SYN packet. Signed-off-by: Eric Dumazet Cc: Perry Lorier Cc: Matt Mathis Cc: Yuchung Cheng Cc: Neal Cardwell Cc: Wilmer van der Gaast Cc: Ankur Jain Cc: Tom Herbert Cc: Dave Täht Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings Cc: Florian Westphal

tcp: force a dst refcount when prequeue packet

2013-05-30T13:35:11+00:00

[ Upstream commit 093162553c33e9479283e107b4431378271c735d ] Before escaping RCU protected section and adding packet into prequeue, make sure the dst is refcounted. Reported-by: Mike Galbraith Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

tcp: implement RFC 5961 3.2

2013-01-16T01:13:25+00:00

[ Upstream commit 282f23c6ee343126156dd41218b22ece96d747e3 ] Implement the RFC 5691 mitigation against Blind Reset attack using RST bit. Idea is to validate incoming RST sequence, to match RCV.NXT value, instead of previouly accepted window : (RCV.NXT <= SEG.SEQ < RCV.NXT+RCV.WND) If sequence is in window but not an exact match, send a "challenge ACK", so that the other part can resend an RST with the appropriate sequence. Add a new sysctl, tcp_challenge_ack_limit, to limit number of challenge ACK sent per second. Add a new SNMP counter to count number of challenge acks sent. (netstat -s | grep TCPChallengeACK) Signed-off-by: Eric Dumazet Cc: Kiran Kumar Kella Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

net: make the tcp and udp file_operations for the /proc stuff const

2011-11-01T21:56:14+00:00

the tcp and udp code creates a set of struct file_operations at runtime while it can also be done at compile time, with the added benefit of then having these file operations be const. the trickiest part was to get the "THIS_MODULE" reference right; the naive method of declaring a struct in the place of registration would not work for this reason. Signed-off-by: Arjan van de Ven Signed-off-by: David S. Miller

TCP: remove TCP_DEBUG

2011-10-24T21:36:08+00:00

It was enabled by default and the messages guarded by the define are useful. Signed-off-by: Flavio Leitner Signed-off-by: David S. Miller

tcp: md5: add more const attributes

2011-10-24T06:46:04+00:00

Now tcp_md5_hash_header() has a const tcphdr argument, we can add more const attributes to callers. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller