diff mbox series

[net] net/packet: fix slab-out-of-bounds access in packet_recvmsg()

Message ID 20220312232958.3535620-1-eric.dumazet@gmail.com (mailing list archive)
State Accepted
Commit c700525fcc06b05adfea78039de02628af79e07a
Delegated to: Netdev Maintainers
Headers show
Series [net] net/packet: fix slab-out-of-bounds access in packet_recvmsg() | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers fail 1 blamed authors not CCed: ebiederm@xmission.com; 2 maintainers not CCed: pablo@netfilter.org ebiederm@xmission.com
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
netdev/checkpatch warning WARNING: Possible repeated word: 'Google' WARNING: line length of 82 exceeds 80 columns WARNING: line length of 87 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Eric Dumazet March 12, 2022, 11:29 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

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>
---
 net/packet/af_packet.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Comments

patchwork-bot+netdevbpf@kernel.org March 15, 2022, 5:40 a.m. UTC | #1 
Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Sat, 12 Mar 2022 15:29:58 -0800 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> 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.
> 
> [...]

Here is the summary with links:
  - [net] net/packet: fix slab-out-of-bounds access in packet_recvmsg()
    https://git.kernel.org/netdev/net/c/c700525fcc06

You are awesome, thank you!
diff mbox series

Patch

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1b93ce1a5600d73284ccb2a2de6c6dbdd9e8dd3c..c39c09899fd0e1c5e7572eda554752e76c481aff 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2318,8 +2318,11 @@  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) {
@@ -3464,6 +3467,8 @@  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
@@ -3486,6 +3491,10 @@  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);
 	}