path: root/net/ipv4/udp.c
diff options
authorEric Dumazet <edumazet@google.com>2019-10-24 11:43:31 -0700
committerDavid S. Miller <davem@davemloft.net>2019-10-28 13:53:40 -0700
commita793183caa9afae907a0d7ddd2ffd57329369bf5 (patch)
treeea8d3071c0999d6e0ede0e3fbb4da5da3aeacc3c /net/ipv4/udp.c
parentnet: dpaa2: Use the correct style for SPDX License Identifier (diff)
udp: fix data-race in udp_set_dev_scratch()
KCSAN reported a data-race in udp_set_dev_scratch() [1] The issue here is that we must not write over skb fields if skb is shared. A similar issue has been fixed in commit 89c22d8c3b27 ("net: Fix skb csum races when peeking") While we are at it, use a helper only dealing with udp_skb_scratch(skb)->csum_unnecessary, as this allows udp_set_dev_scratch() to be called once and thus inlined. [1] BUG: KCSAN: data-race in udp_set_dev_scratch / udpv6_recvmsg write to 0xffff888120278317 of 1 bytes by task 10411 on cpu 1: udp_set_dev_scratch+0xea/0x200 net/ipv4/udp.c:1308 __first_packet_length+0x147/0x420 net/ipv4/udp.c:1556 first_packet_length+0x68/0x2a0 net/ipv4/udp.c:1579 udp_poll+0xea/0x110 net/ipv4/udp.c:2720 sock_poll+0xed/0x250 net/socket.c:1256 vfs_poll include/linux/poll.h:90 [inline] do_select+0x7d0/0x1020 fs/select.c:534 core_sys_select+0x381/0x550 fs/select.c:677 do_pselect.constprop.0+0x11d/0x160 fs/select.c:759 __do_sys_pselect6 fs/select.c:784 [inline] __se_sys_pselect6 fs/select.c:769 [inline] __x64_sys_pselect6+0x12e/0x170 fs/select.c:769 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 read to 0xffff888120278317 of 1 bytes by task 10413 on cpu 0: udp_skb_csum_unnecessary include/net/udp.h:358 [inline] udpv6_recvmsg+0x43e/0xe90 net/ipv6/udp.c:310 inet6_recvmsg+0xbb/0x240 net/ipv6/af_inet6.c:592 sock_recvmsg_nosec+0x5c/0x70 net/socket.c:871 ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480 do_recvmmsg+0x19a/0x5c0 net/socket.c:2601 __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680 __do_sys_recvmmsg net/socket.c:2703 [inline] __se_sys_recvmmsg net/socket.c:2696 [inline] __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 10413 Comm: syz-executor.0 Not tainted 5.4.0-rc3+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: 2276f58ac589 ("udp: use a separate rx queue for packet reception") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Cc: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/udp.c')
1 files changed, 15 insertions, 4 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 345a3d43f5a6..d1ed160af202 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1316,6 +1316,20 @@ static void udp_set_dev_scratch(struct sk_buff *skb)
scratch->_tsize_state |= UDP_SKB_IS_STATELESS;
+static void udp_skb_csum_unnecessary_set(struct sk_buff *skb)
+ /* We come here after udp_lib_checksum_complete() returned 0.
+ * This means that __skb_checksum_complete() might have
+ * set skb->csum_valid to 1.
+ * On 64bit platforms, we can set csum_unnecessary
+ * to true, but only if the skb is not shared.
+ */
+#if BITS_PER_LONG == 64
+ if (!skb_shared(skb))
+ udp_skb_scratch(skb)->csum_unnecessary = true;
static int udp_skb_truesize(struct sk_buff *skb)
return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
@@ -1550,10 +1564,7 @@ static struct sk_buff *__first_packet_length(struct sock *sk,
*total += skb->truesize;
} else {
- /* the csum related bits could be changed, refresh
- * the scratch area
- */
- udp_set_dev_scratch(skb);
+ udp_skb_csum_unnecessary_set(skb);