af_packet: Fix warning of fortified memcpy() in packet_getname().
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, let's add a flex array member union-ed with
sll_addr.
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>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230724213425.22920-3-kuniyu@amazon.com
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>