diff options
| author | David Herrmann <dh.herrmann@gmail.com> | 2015-10-21 11:47:43 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-10-22 07:18:28 -0700 |
| commit | 47191d65b647af5eb5c82ede70ed4c24b1e93ef4 (patch) | |
| tree | 864eabcb29d69af1397290e7ffa926207eee01ff | |
| parent | 34e45ad9378c31ef2b59e8bd63d62f0ca8e719a3 (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.c | 4 |
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: |