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| author | Deepa Dinamani | 2018-12-28 03:55:09 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2019-01-09 17:38:33 +0100 |
| commit | 60f05dddf1eb5db3595e011f293eefa37cefae2e (patch) | |
| tree | 765641af3323c124a23254921d4c604016410805 /net/core | |
| parent | sctp: initialize sin6_flowinfo for ipv6 addrs in sctp_inet6addr_event (diff) | |
| download | kernel-qcow2-linux-60f05dddf1eb5db3595e011f293eefa37cefae2e.tar.gz kernel-qcow2-linux-60f05dddf1eb5db3595e011f293eefa37cefae2e.tar.xz kernel-qcow2-linux-60f05dddf1eb5db3595e011f293eefa37cefae2e.zip | |
sock: Make sock->sk_stamp thread-safe
[ Upstream commit 3a0ed3e9619738067214871e9cb826fa23b2ddb9 ]
Al Viro mentioned (Message-ID
<20170626041334.GZ10672@ZenIV.linux.org.uk>)
that there is probably a race condition
lurking in accesses of sk_stamp on 32-bit machines.
sock->sk_stamp is of type ktime_t which is always an s64.
On a 32 bit architecture, we might run into situations of
unsafe access as the access to the field becomes non atomic.
Use seqlocks for synchronization.
This allows us to avoid using spinlocks for readers as
readers do not need mutual exclusion.
Another approach to solve this is to require sk_lock for all
modifications of the timestamps. The current approach allows
for timestamps to have their own lock: sk_stamp_lock.
This allows for the patch to not compete with already
existing critical sections, and side effects are limited
to the paths in the patch.
The addition of the new field maintains the data locality
optimizations from
commit 9115e8cd2a0c ("net: reorganize struct sock for better data
locality")
Note that all the instances of the sk_stamp accesses
are either through the ioctl or the syscall recvmsg.
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/sock.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/net/core/sock.c b/net/core/sock.c index 748765e35423..5a8a3b76832f 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2803,6 +2803,9 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT; sk->sk_stamp = SK_DEFAULT_STAMP; +#if BITS_PER_LONG==32 + seqlock_init(&sk->sk_stamp_seq); +#endif atomic_set(&sk->sk_zckey, 0); #ifdef CONFIG_NET_RX_BUSY_POLL @@ -2902,12 +2905,13 @@ int sock_get_timestamp(struct sock *sk, struct timeval __user *userstamp) struct timeval tv; sock_enable_timestamp(sk, SOCK_TIMESTAMP); - tv = ktime_to_timeval(sk->sk_stamp); + tv = ktime_to_timeval(sock_read_timestamp(sk)); if (tv.tv_sec == -1) return -ENOENT; if (tv.tv_sec == 0) { - sk->sk_stamp = ktime_get_real(); - tv = ktime_to_timeval(sk->sk_stamp); + ktime_t kt = ktime_get_real(); + sock_write_timestamp(sk, kt); + tv = ktime_to_timeval(kt); } return copy_to_user(userstamp, &tv, sizeof(tv)) ? -EFAULT : 0; } @@ -2918,11 +2922,12 @@ int sock_get_timestampns(struct sock *sk, struct timespec __user *userstamp) struct timespec ts; sock_enable_timestamp(sk, SOCK_TIMESTAMP); - ts = ktime_to_timespec(sk->sk_stamp); + ts = ktime_to_timespec(sock_read_timestamp(sk)); if (ts.tv_sec == -1) return -ENOENT; if (ts.tv_sec == 0) { - sk->sk_stamp = ktime_get_real(); + ktime_t kt = ktime_get_real(); + sock_write_timestamp(sk, kt); ts = ktime_to_timespec(sk->sk_stamp); } return copy_to_user(userstamp, &ts, sizeof(ts)) ? -EFAULT : 0; |