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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>
This commit is contained in:
Herbert Xu 2009-01-30 14:12:06 -08:00 committed by David S. Miller
parent 1974cc205e
commit 905db44087
1 changed files with 7 additions and 2 deletions
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9
net/packet/af_packet.c
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@ -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 @@ struct packet_sock {
#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 @@ static int packet_create(struct net *net, struct socket *sock, int protocol)
*/
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 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
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 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
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 @@ static int packet_mmap(struct file *file, struct socket *sock, struct vm_area_st
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 @@ static int packet_mmap(struct file *file, struct socket *sock, struct vm_area_st
err = 0;
out:
release_sock(sk);
mutex_unlock(&po->pg_vec_lock);
return err;
}
#endif