From a0ade8404c3bc2bf2631cb0f20d372eed22d9d96 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Mon, 24 Jul 2023 14:34:25 -0700 Subject: [PATCH] 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 Suggested-by: Kees Cook Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230724213425.22920-3-kuniyu@amazon.com Reviewed-by: Simon Horman Reviewed-by: Kees Cook Signed-off-by: Jakub Kicinski --- include/uapi/linux/if_packet.h | 6 +++++- net/packet/af_packet.c | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h index 9efc42382fdb..4d0ad22f83b5 100644 --- a/include/uapi/linux/if_packet.h +++ b/include/uapi/linux/if_packet.h @@ -18,7 +18,11 @@ struct sockaddr_ll { unsigned short sll_hatype; unsigned char sll_pkttype; unsigned char sll_halen; - unsigned char sll_addr[8]; + union { + unsigned char sll_addr[8]; + /* Actual length is in sll_halen. */ + __DECLARE_FLEX_ARRAY(unsigned char, sll_addr_flex); + }; }; /* Packet types */ diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 85ff90a03b0c..8e3ddec4c3d5 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3601,7 +3601,7 @@ 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); + memcpy(sll->sll_addr_flex, dev->dev_addr, dev->addr_len); } else { sll->sll_hatype = 0; /* Bad: we have no ARPHRD_UNSPEC */ sll->sll_halen = 0;