path: root/net/core/sock.c
diff options
authorDeepa Dinamani <deepa.kernel@gmail.com>2018-12-27 18:55:09 -0800
committerDavid S. Miller <davem@davemloft.net>2019-01-01 09:47:59 -0800
commit3a0ed3e9619738067214871e9cb826fa23b2ddb9 (patch)
treef27788a1eb07823c642631cb4d27aa0c052e3095 /net/core/sock.c
parentibmveth: fix DMA unmap error in ibmveth_xmit_start error path (diff)
sock: Make sock->sk_stamp thread-safe
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>
Diffstat (limited to 'net/core/sock.c')
1 files changed, 10 insertions, 5 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index f00902c532cc..6aa2e7e0b4fb 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2751,6 +2751,9 @@ 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);
atomic_set(&sk->sk_zckey, 0);
@@ -2850,12 +2853,13 @@ 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;
@@ -2866,11 +2870,12 @@ 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;