packet: Avoid lock_sock in mmap handler
As the mmap handler gets called under mmap_sem, and we may grab
mmap_sem elsewhere under the socket lock to access user data, we
should avoid grabbing the socket lock in the mmap handler.
Since the only thing we care about in the mmap handler is for
pg_vec* to be invariant, i.e., to exclude packet_set_ring, we
can achieve this by simply using a new mutex.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Martin MOKREJŠ <mmokrejs@ribosome.natur.cuni.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 5f94db2..9454d4a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -77,6 +77,7 @@
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/init.h>
+#include <linux/mutex.h>
#ifdef CONFIG_INET
#include <net/inet_common.h>
@@ -175,6 +176,7 @@
#endif
struct packet_type prot_hook;
spinlock_t bind_lock;
+ struct mutex pg_vec_lock;
unsigned int running:1, /* prot_hook is attached*/
auxdata:1,
origdev:1;
@@ -1069,6 +1071,7 @@
*/
spin_lock_init(&po->bind_lock);
+ mutex_init(&po->pg_vec_lock);
po->prot_hook.func = packet_rcv;
if (sock->type == SOCK_PACKET)
@@ -1865,6 +1868,7 @@
synchronize_net();
err = -EBUSY;
+ mutex_lock(&po->pg_vec_lock);
if (closing || atomic_read(&po->mapped) == 0) {
err = 0;
#define XC(a, b) ({ __typeof__ ((a)) __t; __t = (a); (a) = (b); __t; })
@@ -1886,6 +1890,7 @@
if (atomic_read(&po->mapped))
printk(KERN_DEBUG "packet_mmap: vma is busy: %d\n", atomic_read(&po->mapped));
}
+ mutex_unlock(&po->pg_vec_lock);
spin_lock(&po->bind_lock);
if (was_running && !po->running) {
@@ -1918,7 +1923,7 @@
size = vma->vm_end - vma->vm_start;
- lock_sock(sk);
+ mutex_lock(&po->pg_vec_lock);
if (po->pg_vec == NULL)
goto out;
if (size != po->pg_vec_len*po->pg_vec_pages*PAGE_SIZE)
@@ -1941,7 +1946,7 @@
err = 0;
out:
- release_sock(sk);
+ mutex_unlock(&po->pg_vec_lock);
return err;
}
#endif
