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authorDavid Herrmann <dh.herrmann@gmail.com>2015-10-21 11:47:43 +0200
committerDavid S. Miller <davem@davemloft.net>2015-10-22 07:18:28 -0700
commit47191d65b647af5eb5c82ede70ed4c24b1e93ef4 (patch)
tree864eabcb29d69af1397290e7ffa926207eee01ff
parent34e45ad9378c31ef2b59e8bd63d62f0ca8e719a3 (diff)
netlink: fix locking around NETLINK_LIST_MEMBERSHIPS
Currently, NETLINK_LIST_MEMBERSHIPS grabs the netlink table while copying the membership state to user-space. However, grabing the netlink table is effectively a write_lock_irq(), and as such we should not be triggering page-faults in the critical section. This can be easily reproduced by the following snippet: int s = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); void *p = mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); int r = getsockopt(s, 0x10e, 9, p, (void*)((char*)p + 4092)); This should work just fine, but currently triggers EFAULT and a possible WARN_ON below handle_mm_fault(). Fix this by reducing locking of NETLINK_LIST_MEMBERSHIPS to a read-side lock. The write-lock was overkill in the first place, and the read-lock allows page-faults just fine. Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/netlink/af_netlink.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 0a49a8c7c564..fafe33bdb619 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2371,7 +2371,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
int pos, idx, shift;
err = 0;
- netlink_table_grab();
+ netlink_lock_table();
for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
if (len - pos < sizeof(u32))
break;
@@ -2386,7 +2386,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
}
if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
err = -EFAULT;
- netlink_table_ungrab();
+ netlink_unlock_table();
break;
}
case NETLINK_CAP_ACK: