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authorEric Dumazet <edumazet@google.com>2022-03-12 15:29:58 -0800
committerJakub Kicinski <kuba@kernel.org>2022-03-14 22:08:34 -0700
commitc700525fcc06b05adfea78039de02628af79e07a (patch)
tree025edd239e9fdb02e96f2a4dfa79cca6cf55dac2 /net/packet
parent0f8946ae704ac6880c590beb91bc3a732595a28a (diff)
net/packet: fix slab-out-of-bounds access in packet_recvmsg()
syzbot found that when an AF_PACKET socket is using PACKET_COPY_THRESH and mmap operations, tpacket_rcv() is queueing skbs with garbage in skb->cb[], triggering a too big copy [1] Presumably, users of af_packet using mmap() already gets correct metadata from the mapped buffer, we can simply make sure to clear 12 bytes that might be copied to user space later. BUG: KASAN: stack-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline] BUG: KASAN: stack-out-of-bounds in packet_recvmsg+0x56c/0x1150 net/packet/af_packet.c:3489 Write of size 165 at addr ffffc9000385fb78 by task syz-executor233/3631 CPU: 0 PID: 3631 Comm: syz-executor233 Not tainted 5.17.0-rc7-syzkaller-02396-g0b3660695e80 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0xf/0x336 mm/kasan/report.c:255 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189 memcpy+0x39/0x60 mm/kasan/shadow.c:66 memcpy include/linux/fortify-string.h:225 [inline] packet_recvmsg+0x56c/0x1150 net/packet/af_packet.c:3489 sock_recvmsg_nosec net/socket.c:948 [inline] sock_recvmsg net/socket.c:966 [inline] sock_recvmsg net/socket.c:962 [inline] ____sys_recvmsg+0x2c4/0x600 net/socket.c:2632 ___sys_recvmsg+0x127/0x200 net/socket.c:2674 __sys_recvmsg+0xe2/0x1a0 net/socket.c:2704 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fdfd5954c29 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffcf8e71e48 EFLAGS: 00000246 ORIG_RAX: 000000000000002f RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fdfd5954c29 RDX: 0000000000000000 RSI: 0000000020000500 RDI: 0000000000000005 RBP: 0000000000000000 R08: 000000000000000d R09: 000000000000000d R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcf8e71e60 R13: 00000000000f4240 R14: 000000000000c1ff R15: 00007ffcf8e71e54 </TASK> addr ffffc9000385fb78 is located in stack of task syz-executor233/3631 at offset 32 in frame: ____sys_recvmsg+0x0/0x600 include/linux/uio.h:246 this frame has 1 object: [32, 160) 'addr' Memory state around the buggy address: ffffc9000385fa80: 00 04 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 ffffc9000385fb00: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 >ffffc9000385fb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f3 ^ ffffc9000385fc00: f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 f1 ffffc9000385fc80: f1 f1 f1 00 f2 f2 f2 00 f2 f2 f2 00 00 00 00 00 ================================================================== Fixes: 0fb375fb9b93 ("[AF_PACKET]: Allow for > 8 byte hardware addresses.") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Link: https://lore.kernel.org/r/20220312232958.3535620-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index ab87f22cc7ec..a7273af2d900 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2317,8 +2317,11 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
copy_skb = skb_get(skb);
skb_head = skb->data;
}
- if (copy_skb)
+ if (copy_skb) {
+ memset(&PACKET_SKB_CB(copy_skb)->sa.ll, 0,
+ sizeof(PACKET_SKB_CB(copy_skb)->sa.ll));
skb_set_owner_r(copy_skb, sk);
+ }
}
snaplen = po->rx_ring.frame_size - macoff;
if ((int)snaplen < 0) {
@@ -3462,6 +3465,8 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
sock_recv_ts_and_drops(msg, sk, skb);
if (msg->msg_name) {
+ const size_t max_len = min(sizeof(skb->cb),
+ sizeof(struct sockaddr_storage));
int copy_len;
/* If the address length field is there to be filled
@@ -3484,6 +3489,10 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
msg->msg_namelen = sizeof(struct sockaddr_ll);
}
}
+ if (WARN_ON_ONCE(copy_len > max_len)) {
+ copy_len = max_len;
+ msg->msg_namelen = copy_len;
+ }
memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa, copy_len);
}