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authorOlof Johansson <olof@lixom.net>2007-10-19 08:48:39 +0400
committerDavid S. Miller <davem@davemloft.net>2007-10-19 08:48:39 +0400
commit9b013e05e0289c190a53d78ca029e2f21c0e4485 (patch)
tree4ccb15877b7d950946ff2fe312211b71493878a8
parent4fa4d23fa20de67df919030c1216295664866ad7 (diff)
downloadlinux-9b013e05e0289c190a53d78ca029e2f21c0e4485.tar.xz
[NET]: Fix bug in sk_filter race cures.
Looks like this might be causing problems, at least for me on ppc. This happened during a normal boot, right around first interface config/dhcp run.. cpu 0x0: Vector: 300 (Data Access) at [c00000000147b820] pc: c000000000435e5c: .sk_filter_delayed_uncharge+0x1c/0x60 lr: c0000000004360d0: .sk_attach_filter+0x170/0x180 sp: c00000000147baa0 msr: 9000000000009032 dar: 4 dsisr: 40000000 current = 0xc000000004780fa0 paca = 0xc000000000650480 pid = 1295, comm = dhclient3 0:mon> t [c00000000147bb20] c0000000004360d0 .sk_attach_filter+0x170/0x180 [c00000000147bbd0] c000000000418988 .sock_setsockopt+0x788/0x7f0 [c00000000147bcb0] c000000000438a74 .compat_sys_setsockopt+0x4e4/0x5a0 [c00000000147bd90] c00000000043955c .compat_sys_socketcall+0x25c/0x2b0 [c00000000147be30] c000000000007508 syscall_exit+0x0/0x40 --- Exception: c01 (System Call) at 000000000ff618d8 SP (fffdf040) is in userspace 0:mon> I.e. null pointer deref at sk_filter_delayed_uncharge+0x1c: 0:mon> di $.sk_filter_delayed_uncharge c000000000435e40 7c0802a6 mflr r0 c000000000435e44 fbc1fff0 std r30,-16(r1) c000000000435e48 7c8b2378 mr r11,r4 c000000000435e4c ebc2cdd0 ld r30,-12848(r2) c000000000435e50 f8010010 std r0,16(r1) c000000000435e54 f821ff81 stdu r1,-128(r1) c000000000435e58 380300a4 addi r0,r3,164 c000000000435e5c 81240004 lwz r9,4(r4) That's the deref of fp: static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp) { unsigned int size = sk_filter_len(fp); ... That is called from sk_attach_filter(): ... rcu_read_lock_bh(); old_fp = rcu_dereference(sk->sk_filter); rcu_assign_pointer(sk->sk_filter, fp); rcu_read_unlock_bh(); sk_filter_delayed_uncharge(sk, old_fp); return 0; ... So, looks like rcu_dereference() returned NULL. I don't know the filter code at all, but it seems like it might be a valid case? sk_detach_filter() seems to handle a NULL sk_filter, at least. So, this needs review by someone who knows the filter, but it fixes the problem for me: Signed-off-by: Olof Johansson <olof@lixom.net> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/filter.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index 1f0068eae501..e0a06942c025 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -447,7 +447,8 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
rcu_assign_pointer(sk->sk_filter, fp);
rcu_read_unlock_bh();
- sk_filter_delayed_uncharge(sk, old_fp);
+ if (old_fp)
+ sk_filter_delayed_uncharge(sk, old_fp);
return 0;
}