| Message ID | 20240429151605.2055465-1-syoshida@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] ipv4: Fix uninit-value access in __ip_make_skb() | expand |
Sorry, I forgot to add "v2" to the prefix. I will repost this. On Tue, 30 Apr 2024 00:16:05 +0900, Shigeru Yoshida wrote: > KMSAN reported uninit-value access in __ip_make_skb() [1]. __ip_make_skb() > tests HDRINCL to know if the skb has icmphdr. However, HDRINCL can cause a > race condition. If calling setsockopt(2) with IP_HDRINCL changes HDRINCL > while __ip_make_skb() is running, the function will access icmphdr in the > skb even if it is not included. This causes the issue reported by KMSAN. > > Check FLOWI_FLAG_KNOWN_NH on fl4->flowi4_flags instead of testing HDRINCL > on the socket. > > Also, fl4->fl4_icmp_type and fl4->fl4_icmp_code are not initialized. These > are union in struct flowi4 and are implicitly initialized by > flowi4_init_output(), but we should not rely on specific union layout. > > Initialize these explicitly in raw_sendmsg(). > > [1] > BUG: KMSAN: uninit-value in __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481 > __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481 > ip_finish_skb include/net/ip.h:243 [inline] > ip_push_pending_frames+0x4c/0x5c0 net/ipv4/ip_output.c:1508 > raw_sendmsg+0x2381/0x2690 net/ipv4/raw.c:654 > inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851 > sock_sendmsg_nosec net/socket.c:730 [inline] > __sock_sendmsg+0x274/0x3c0 net/socket.c:745 > __sys_sendto+0x62c/0x7b0 net/socket.c:2191 > __do_sys_sendto net/socket.c:2203 [inline] > __se_sys_sendto net/socket.c:2199 [inline] > __x64_sys_sendto+0x130/0x200 net/socket.c:2199 > do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x6d/0x75 > > Uninit was created at: > slab_post_alloc_hook mm/slub.c:3804 [inline] > slab_alloc_node mm/slub.c:3845 [inline] > kmem_cache_alloc_node+0x5f6/0xc50 mm/slub.c:3888 > kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:577 > __alloc_skb+0x35a/0x7c0 net/core/skbuff.c:668 > alloc_skb include/linux/skbuff.h:1318 [inline] > __ip_append_data+0x49ab/0x68c0 net/ipv4/ip_output.c:1128 > ip_append_data+0x1e7/0x260 net/ipv4/ip_output.c:1365 > raw_sendmsg+0x22b1/0x2690 net/ipv4/raw.c:648 > inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851 > sock_sendmsg_nosec net/socket.c:730 [inline] > __sock_sendmsg+0x274/0x3c0 net/socket.c:745 > __sys_sendto+0x62c/0x7b0 net/socket.c:2191 > __do_sys_sendto net/socket.c:2203 [inline] > __se_sys_sendto net/socket.c:2199 [inline] > __x64_sys_sendto+0x130/0x200 net/socket.c:2199 > do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x6d/0x75 > > CPU: 1 PID: 15709 Comm: syz-executor.7 Not tainted 6.8.0-11567-gb3603fcb79b1 #25 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014 > > Fixes: 99e5acae193e ("ipv4: Fix potential uninit variable access bug in __ip_make_skb()") > Reported-by: syzkaller <syzkaller@googlegroups.com> > Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> > --- > v1->v2: https://lore.kernel.org/all/20240324050554.1609460-1-syoshida@redhat.com/ > - Explicitly initialize fl4->fl4_icmp_type and fl4->fl4_icmp_code because > we should not rely on a specific union layout. > --- > net/ipv4/ip_output.c | 2 +- > net/ipv4/raw.c | 3 +++ > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c > index 1fe794967211..39229fd0601a 100644 > --- a/net/ipv4/ip_output.c > +++ b/net/ipv4/ip_output.c > @@ -1473,7 +1473,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk, > * by icmp_hdr(skb)->type. > */ > if (sk->sk_type == SOCK_RAW && > - !inet_test_bit(HDRINCL, sk)) > + !(fl4->flowi4_flags & FLOWI_FLAG_KNOWN_NH)) > icmp_type = fl4->fl4_icmp_type; > else > icmp_type = icmp_hdr(skb)->type; > diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c > index dcb11f22cbf2..4cb43401e0e0 100644 > --- a/net/ipv4/raw.c > +++ b/net/ipv4/raw.c > @@ -612,6 +612,9 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) > (hdrincl ? FLOWI_FLAG_KNOWN_NH : 0), > daddr, saddr, 0, 0, sk->sk_uid); > > + fl4.fl4_icmp_type = 0; > + fl4.fl4_icmp_code = 0; > + > if (!hdrincl) { > rfv.msg = msg; > rfv.hlen = 0; > -- > 2.44.0 >
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 1fe794967211..39229fd0601a 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -1473,7 +1473,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk, * by icmp_hdr(skb)->type. */ if (sk->sk_type == SOCK_RAW && - !inet_test_bit(HDRINCL, sk)) + !(fl4->flowi4_flags & FLOWI_FLAG_KNOWN_NH)) icmp_type = fl4->fl4_icmp_type; else icmp_type = icmp_hdr(skb)->type; diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c index dcb11f22cbf2..4cb43401e0e0 100644 --- a/net/ipv4/raw.c +++ b/net/ipv4/raw.c @@ -612,6 +612,9 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) (hdrincl ? FLOWI_FLAG_KNOWN_NH : 0), daddr, saddr, 0, 0, sk->sk_uid); + fl4.fl4_icmp_type = 0; + fl4.fl4_icmp_code = 0; + if (!hdrincl) { rfv.msg = msg; rfv.hlen = 0;
KMSAN reported uninit-value access in __ip_make_skb() [1]. __ip_make_skb() tests HDRINCL to know if the skb has icmphdr. However, HDRINCL can cause a race condition. If calling setsockopt(2) with IP_HDRINCL changes HDRINCL while __ip_make_skb() is running, the function will access icmphdr in the skb even if it is not included. This causes the issue reported by KMSAN. Check FLOWI_FLAG_KNOWN_NH on fl4->flowi4_flags instead of testing HDRINCL on the socket. Also, fl4->fl4_icmp_type and fl4->fl4_icmp_code are not initialized. These are union in struct flowi4 and are implicitly initialized by flowi4_init_output(), but we should not rely on specific union layout. Initialize these explicitly in raw_sendmsg(). [1] BUG: KMSAN: uninit-value in __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481 __ip_make_skb+0x2b74/0x2d20 net/ipv4/ip_output.c:1481 ip_finish_skb include/net/ip.h:243 [inline] ip_push_pending_frames+0x4c/0x5c0 net/ipv4/ip_output.c:1508 raw_sendmsg+0x2381/0x2690 net/ipv4/raw.c:654 inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x274/0x3c0 net/socket.c:745 __sys_sendto+0x62c/0x7b0 net/socket.c:2191 __do_sys_sendto net/socket.c:2203 [inline] __se_sys_sendto net/socket.c:2199 [inline] __x64_sys_sendto+0x130/0x200 net/socket.c:2199 do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x6d/0x75 Uninit was created at: slab_post_alloc_hook mm/slub.c:3804 [inline] slab_alloc_node mm/slub.c:3845 [inline] kmem_cache_alloc_node+0x5f6/0xc50 mm/slub.c:3888 kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:577 __alloc_skb+0x35a/0x7c0 net/core/skbuff.c:668 alloc_skb include/linux/skbuff.h:1318 [inline] __ip_append_data+0x49ab/0x68c0 net/ipv4/ip_output.c:1128 ip_append_data+0x1e7/0x260 net/ipv4/ip_output.c:1365 raw_sendmsg+0x22b1/0x2690 net/ipv4/raw.c:648 inet_sendmsg+0x27b/0x2a0 net/ipv4/af_inet.c:851 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x274/0x3c0 net/socket.c:745 __sys_sendto+0x62c/0x7b0 net/socket.c:2191 __do_sys_sendto net/socket.c:2203 [inline] __se_sys_sendto net/socket.c:2199 [inline] __x64_sys_sendto+0x130/0x200 net/socket.c:2199 do_syscall_64+0xd8/0x1f0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x6d/0x75 CPU: 1 PID: 15709 Comm: syz-executor.7 Not tainted 6.8.0-11567-gb3603fcb79b1 #25 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014 Fixes: 99e5acae193e ("ipv4: Fix potential uninit variable access bug in __ip_make_skb()") Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> --- v1->v2: https://lore.kernel.org/all/20240324050554.1609460-1-syoshida@redhat.com/ - Explicitly initialize fl4->fl4_icmp_type and fl4->fl4_icmp_code because we should not rely on a specific union layout. --- net/ipv4/ip_output.c | 2 +- net/ipv4/raw.c | 3 +++ 2 files changed, 4 insertions(+), 1 deletion(-)