From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Kees Cook <keescook@chromium.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
"Breno Leitao" <leitao@debian.org>,
Kuniyuki Iwashima <kuniyu@amazon.com>,
"Kuniyuki Iwashima" <kuni1840@gmail.com>,
<netdev@vger.kernel.org>, syzkaller <syzkaller@googlegroups.com>
Subject: [PATCH v2 net 2/2] af_packet: Fix warning of fortified memcpy() in packet_getname().
Date: Wed, 19 Jul 2023 17:44:10 -0700 [thread overview]
Message-ID: <20230720004410.87588-3-kuniyu@amazon.com> (raw)
In-Reply-To: <20230720004410.87588-1-kuniyu@amazon.com>
syzkaller found a warning in packet_getname() [0], where we try to
copy 16 bytes to sockaddr_ll.sll_addr[8].
Some devices (ip6gre, vti6, ip6tnl) have 16 bytes address expressed
by struct in6_addr. Also, Infiniband has 32 bytes as MAX_ADDR_LEN.
The write seems to overflow, but actually not since we use struct
sockaddr_storage defined in __sys_getsockname() and its size is 128
(_K_SS_MAXSIZE) bytes. Thus, we have sufficient room after sll_addr[]
as __data[].
To avoid the warning, we need to let __fortify_memcpy_chk() know the
actual buffer size.
Another option would be to use strncpy() and limit the copied length
to sizeof(sll_addr), but it will return the partial address and break
an application that passes sockaddr_storage to getsockname().
[0]:
memcpy: detected field-spanning write (size 16) of single field "sll->sll_addr" at net/packet/af_packet.c:3604 (size 8)
WARNING: CPU: 0 PID: 255 at net/packet/af_packet.c:3604 packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604
Modules linked in:
CPU: 0 PID: 255 Comm: syz-executor750 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #4
Hardware name: linux,dummy-virt (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604
lr : packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604
sp : ffff800089887bc0
x29: ffff800089887bc0 x28: ffff000010f80f80 x27: 0000000000000003
x26: dfff800000000000 x25: ffff700011310f80 x24: ffff800087d55000
x23: dfff800000000000 x22: ffff800089887c2c x21: 0000000000000010
x20: ffff00000de08310 x19: ffff800089887c20 x18: ffff800086ab1630
x17: 20646c6569662065 x16: 6c676e697320666f x15: 0000000000000001
x14: 1fffe0000d56d7ca x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000 x9 : 3e60944c3da92b00
x8 : 3e60944c3da92b00 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff8000898874f8 x4 : ffff800086ac99e0 x3 : ffff8000803f8808
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
packet_getname+0x25c/0x3a0 net/packet/af_packet.c:3604
__sys_getsockname+0x168/0x24c net/socket.c:2042
__do_sys_getsockname net/socket.c:2057 [inline]
__se_sys_getsockname net/socket.c:2054 [inline]
__arm64_sys_getsockname+0x7c/0x94 net/socket.c:2054
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x134/0x240 arch/arm64/kernel/syscall.c:139
do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:188
el0_svc+0x2c/0x7c arch/arm64/kernel/entry-common.c:647
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:665
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591
Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
net/packet/af_packet.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 85ff90a03b0c..7f60b78f170f 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3601,7 +3601,12 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
if (dev) {
sll->sll_hatype = dev->type;
sll->sll_halen = dev->addr_len;
- memcpy(sll->sll_addr, dev->dev_addr, dev->addr_len);
+
+ /* Let __fortify_memcpy_chk() know the actual buffer size. */
+ memcpy(((struct sockaddr_storage *)sll)->__data +
+ offsetof(struct sockaddr_ll, sll_addr) -
+ offsetof(struct sockaddr_ll, sll_protocol),
+ dev->dev_addr, dev->addr_len);
} else {
sll->sll_hatype = 0; /* Bad: we have no ARPHRD_UNSPEC */
sll->sll_halen = 0;
--
2.30.2
next prev parent reply other threads:[~2023-07-20 0:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 0:44 [PATCH v2 net 0/2] net: Fix error/warning by -fstrict-flex-arrays=3 Kuniyuki Iwashima
2023-07-20 0:44 ` [PATCH v2 net 1/2] af_unix: Fix fortify_panic() in unix_bind_bsd() Kuniyuki Iwashima
2023-07-20 14:39 ` Kees Cook
2023-07-20 17:09 ` Kuniyuki Iwashima
2023-07-20 0:44 ` Kuniyuki Iwashima [this message]
2023-07-20 14:06 ` [PATCH v2 net 2/2] af_packet: Fix warning of fortified memcpy() in packet_getname() Willem de Bruijn
2023-07-20 15:04 ` Kees Cook
2023-07-20 17:02 ` Kuniyuki Iwashima
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